After Life: Rot Box Detectives


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After Life: Rot Box Detectives

A team of young science detectives investigate rot and decay through a series of experiments and activities, assisted by Dr George McGavin.


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Inside this large, glass box,

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something extraordinary is happening.

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Food is being left to rot for eight weeks

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in our own unique laboratory.

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This is an investigation

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into nature's biggest and best recycler...

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..decay.

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And it's being done on a scale that has never been tried before.

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I'm Dr George McGavin. I'm a biologist with a particular passion for insects.

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The Rot Box detectives, Iona, Rosie,

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Ruaridh, Mram and Jamie

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are going to help me investigate the amazing world of rot and decay.

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'There's bacteria...'

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MACHINE BLEEPING

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Look at that. That really is smelly.

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'..flies...'

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I want to show you the fish. It's been completely eaten out.

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'..and mould.'

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20 or 30 species of fungus?!

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At Rot Box Detective HQ, I'm meeting up with the team.

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-Hi, team.

-ALL: Hi.

-How do you think we made the Rot Box?

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-Great difficulty.

-Yeah, it was quite difficult actually.

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We wanted to make a typical kitchen and garden

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and fill it full of the sort of food you'd have

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if you were having a party.

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We wanted it quite warm, as if it was a hot summer's day

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and we wanted quite humid as well.

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So why do you think we did that?

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The bacteria would come

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because the hotter it is, like if you left a drink out

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for ages, it would go all warm and horrible.

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Exactly. The hotter it is, the faster things happen.

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-All organisms need some form of...?

-Water.

-Water, yes. Exactly.

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So the best conditions for bacteria and fungi

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are hot and sweaty, basically.

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The hotter it is, the faster things rot.

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This giant Rot Box has taken a team of engineers

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and scientists eight months to design and build.

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Conditions inside are now perfect for rot to begin.

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It's hot, humid and there's plenty of air

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so it doesn't take long for the mould to take hold

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and begin breaking down the food.

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By only the second day, there are dramatic changes inside.

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'It's really warm in here,'

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it's 25 degrees. That's like a warm summer day,

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so some things are drying out

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the chilli con carne is already growing a layer of mould.

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That shows there are fungal spores drifting around in the atmosphere

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and settling on food. Over here, the sandwiches

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which originally filled the box,

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up to the top, have sagged down to about half their height.

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-I think it's a fish.

-I thought that was the fish.

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There's two fishes.

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-Eurgh, what's that?

-Oh!

-Where was it?

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-There. It's a dead mouse.

-Eurgh!

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Disgusting!

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The Rot Box Detectives are intrigued and excited by what they see.

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It's time for them to start their own investigations.

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Who knows what an experiment is?

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It's an experiment when you judge something by something else

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and you see the difference maybe.

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Yeah, pretty close.

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If you have a question and you want to find the answer.

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Exactly. It's a controlled test that helps you to see

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if a question you ask is correct or not.

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So how would you design an experiment to investigate

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the effect of temperature on how fast things rot?

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Heat and cold.

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OK, so we have one hot environment and one cold one,

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which is a fridge and the airing cupboard. That's our variable.

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So what will we have to put in those two environments?

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-Something that will...

-Rot.

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Yes! Something that will rot.

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So what sort of things do you think are going to rot easily?

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-Fruit and bread.

-Fruit and bread, yeah.

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-Which do you think would grow the most mould?

-I would say the bread.

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-Yeah.

-Apples.

-Apples, OK.

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Peppers, because in the Rot Box they were all really black and crispy.

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OK, so you've got all these things. What are you going to put them in?

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-Do you think you could put them in a glass box.

-Yeah, OK.

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So you can each have two boxes, one will go in the fridge,

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the other in the airing cupboard where it's warm.

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We've got one variable, which is if it's hot or cold.

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-Everything else should be the same. Why?

-Because it's a fair test.

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Absolutely. It has to be a fair test.

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If you don't have the same things, it's not fair.

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-How does bacteria get into it?

-Good question.

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Well, bacteria is everywhere in the environment.

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We have bacteria all over our hands, even after you've washed them.

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There's bacteria all over this box,

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so the bacteria and the fungi are there,

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we just encourage them to grow.

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Our big Rot Box is also full of bacteria.

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In a matter of hours, they have started to do their work.

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The clearest signs of change are on the chicken.

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In just one day, our time lapse cameras

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show these blotches appearing on its skin,

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I've asked Dr Clare Taylor, a microbiologist, to join me

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and explain what's happening.

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Well, Clare, that chicken is beginning to look

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pretty discoloured.

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It smells a bit as well.

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There's beginning to be a slight whiff. What have you got on this?

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I tell you what I've got a UV light

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so we can take a look more closely at the surface.

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-Now you can't see it.

-No, can't see anything.

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Take a look at that!

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It's glowing! So all these areas are glowing sort of blue.

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Exactly, so where you can see those glowing bits, that's bacteria.

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So even though we can't see them, bacteria are everywhere.

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They're all around us.

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'Now the team and I are going to make our own mini Rot Boxes.'

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LAUGHTER

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Right, two each. Pass them down.

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Two for you, two for you.

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Right, you can put whatever you want in the box,

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as long as both boxes are exactly the same.

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I thought it might be interesting to have one inanimate object,

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like a bolt or something.

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-Will that rot?

-No.

-Why won't it rot?

-Because it's a metal object.

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It's metal, yeah, It isn't alive, is it?

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Fill your boxes!

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So in order for it to be properly scientific,

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we need to write down our names on a piece of paper, the date,

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and describe what we did.

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We have to say what the experiment was supposed to do,

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and what our predictions for the outcome of the experiment is.

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When we take our boxes out of the refrigerator

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and the airing cupboard, we then write down our results, OK?

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'I think the metal thing might get rusty,

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'because when I see the railings they mostly get brown from silver.

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'So I think it might rust a little.

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'I think there will be less mould in the cold one.

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'It might have a little bit of bacteria and a little bit of mould.

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'I think the pepper will rot the most, because when we went to see

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'the Rot Box, in the fruit bowl, the peppers were absolutely disgusting.

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'I don't think that the paper will go mouldy, but I think some

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'of the mould from the apple would probably go a bit onto the paper.

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'I think the potatoes will rot the quickest.'

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-I'm quite excited about this.

-Me too, yeah.

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It'll be really good, this experiment. Really interesting.

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We might even find some undescribed species of fungi or bacteria.

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Who knows? It could happen.

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Back at the big Rot Box,

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the Detectives continue to be amazed by the world of decay.

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But will they see similar results in their mini Rot Boxes?

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Their experiment tests how temperature affects

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the speed of rot. They filled two boxes

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with exactly the same foods. The only variable is temperature.

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One box is in a hot place and one box is in a cold place.

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It's a fair test.

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They've recorded what they did, how they did it

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and what they think might happen.

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What will the detectives discover?

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Inside this large, glass box,

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something extraordinary is happening.

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Food is being left to rot for eight weeks

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in our own unique laboratory

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This is an investigation

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into nature's biggest and best recycler...

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..decay.

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And it's being done on a scale that has never been tried before.

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I'm Dr George McGavin. I'm a biologist with a particular passion for insects.

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The Rot Box detectives, Iona, Rosie,

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Ruaridh, Mram and Jamie

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are going to help me investigate the amazing world of rot and decay.

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'There are flies...'

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Well, there are simply too many flies in here.

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It's becoming quite unpleasant.

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'..bacteria...'

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-Oho!

-Take a look at that.

-It's glowing!

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'..and mould.'

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Even the hamburgers are wrapped up and they're covered in mould. Ooh!

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That might blow at any time.

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Pass them down. Two for you...

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'Four weeks ago, the Rot Box Detectives built their own

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'mini Rot Boxes so they could examine rot

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'more closely for themselves.'

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They wanted to see how temperature affects the speed of rot,

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so they designed a test, an experiment to find the answer.

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They had two boxes each and filled each box with the same things.

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To make the test fair,

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everything was the same except for one variable, which was temperature.

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They wrote down their hypothesis, what they thought would happen.

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I think there'll be less mould in the cold one than the hot one.

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It might have a little bit of bacteria.

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'Scientists often work in laboratories,

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'so we've come along to one to examine the results

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'of our four-week-old Rot Boxes.'

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I want you to meet a friend of mine called Patrick, who's a mycologist.

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That's an expert on fungi.

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Now we can only open the boxes because we're in a lab

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and because Patrick here is a specialist in fungi.

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He will tell us if there's anything harmful to us in these boxes.

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-I suspect there isn't anything that's that harmful.

-It's unlikely.

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As long as we don't sniff or inhale them or eat them, touch them

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and put our fingers in our mouths, we should be fine.

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I know it's going to be very hard for you to resist,

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with your fingers touching things,

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so I think we should all put on gloves.

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OK, let's open the cold box first. So this is Ruaridh's one.

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Well, I can see there is a little bit of mould on the bread there.

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Penicillin probably.

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But everything looks as it would do when it's been fairly freshly made.

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None of it's gone mushy or soggy.

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We'll open the one that's been in the warm temperature.

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-Ooh!

-CHILDREN: Eurgh!

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-That's very different, isn't it?

-The bread has completely gone down

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to a kind of soggy mess.

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The apple looks like it's been poached or something.

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Ruaridh, you've at least shown what you thought was going to happen.

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There's more fungus growing in your hot box, but you were right

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about there being a little bit of fungus in your cold one.

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So this is Jamie's box.

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-Was the bread already this size?

-I don't think it was.

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I think it's shrunken down.

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Why are the bananas pushed in?

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The fungus has taken the moisture out of the banana

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and used it for itself. It's shrunken right down.

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The fungi on my mushroom looks different than the other ones.

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OK, so we have a comparison.

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Fungi often changes depending on what part in their life cycle.

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Sometimes they can change colour in a few days.

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That one's plain white and that one's really bubbly.

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-Is that hard or soft, the mould on there?

-Really soft.

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-It's breaking down.

-Looks like a marshmallow.

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It is just like a marshmallow actually.

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That's the fungal mould that's growing through there.

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Would you say there's anything edible in any of the hot boxes?

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Let's have a look and see.

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No, it's all soft and horrible.

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Because we cut the oranges,

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the fungi and bacteria have got inside them and broken them down.

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But if you had a whole orange in there, it might not rot down.

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But you should still never eat anything in these experiments.

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Back at the big Rot Box,

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Patrick and I are staggered by what we discover.

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Now, this to my, Patrick,

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is one of the most amazing things I've ever seen.

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Look at it! I mean, that was a pile of cheese

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and tomato sandwiches that was up to the top of the box.

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-How many actual species of fungus are here?

-Oh, at least 20 or 30.

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-Maybe more.

-20 or 30 species of fungus?!

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-Look at that. I mean, it's a solid mat.

-Oh, yeah.

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There are the layers of sandwich.

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It's all the way through, it's completely through.

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There aren't many flies here, of course.

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Yeah, it was sealed in the box so the flies couldn't get in.

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Big contrast there to the fruit bowl which was left open.

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A couple of weeks ago, it was really covered in thick layers of fungus.

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-Look at the fly.

-The flies have stripped it bare.

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The flies have gone in there, they've eaten the fungus,

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eaten the spores and really just recycling the fungi.

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Moulds are masters of decay.

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They're a form of fungi, the most versatile

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and important decomposers on the planet.

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Fungi can grow on almost anything.

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In our box, moulds are attacking our fruit and vegetables

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and spread by releasing spores into the air which are like seeds.

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They find new places to settle and grow,

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overwhelming everything in their path, even our meat.

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There are up to 500 spores in every cubic metre of air in your home.

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But they're so small, you can only see them with a microscope.

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Whoa.

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It looks like snow.

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It looks like the fluff on my teddy bear or something like that.

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The white looks like the Antarctic.

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Now this microscope only magnifies things about 100 times.

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But in the Rot Box,

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we had a microscope that could magnify stuff by 7,000 times.

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I want you to take a look at some of the fungi we filmed there.

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This is the kind of mould you might find in your bread,

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magnified by 7,000 times.

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The thread-like stalks are ten times finer than a human hair.

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The fluffy ball shapes at the top are where the spores live.

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Much like dandelion seeds,

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the spores are released into the air and carried to new places to grow.

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You might not always be able to see it, but mould is everywhere.

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Your house alone may contain an unbelievable 1,000 different

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types of mould.

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Patrick, thanks very much.

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It's been a real thrill to be able to use your lab and your expertise.

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-I'm sure we've learned quite a lot, haven't we?

-Yeah.

-So thank you very much.

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Back inside the big Rot Box, mould continues to astound and amaze.

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The Rot Box Detectives have grown their own fantastic fungi

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in their mini Rot Box experiments.

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They found that there was more mould in the hot box than the cold box.

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This is because mould grows faster in warm conditions

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than in cold conditions.

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They prove that their hypothesis,

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which is what they thought might happen, was correct.

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Inside this large, glass box,

0:18:420:18:44

something extraordinary is happening.

0:18:440:18:48

Food is being left to rot for eight weeks

0:18:480:18:51

in our own unique laboratory.

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This is an investigation into nature's biggest and best recycler...

0:18:570:19:04

decay.

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And it's being done on a scale that has never been tried before.

0:19:050:19:10

I'm Dr George McGavin.

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I'm a biologist with a particular passion for insects.

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The Rot Box detectives, Iona, Rosie, Ruaridh, Mram and Jamie

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are going to help me investigate the amazing world of rot and decay.

0:19:230:19:29

'We'll see flies...'

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The burgers that were opened are riddled with maggots.

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'..mould...'

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It's almost a battle zone in your bread bin.

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'..and bacteria.'

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I wonder how many bacteria are on that.

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At Rot Box Detective HQ, we're investigating some really bad smells.

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I've got a challenge for you.

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How can you tell if food is safe to eat, if it's off,

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without actually tasting it?

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Because of the smell?

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Smell is a very good clue.

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Maybe from its looks, because sometimes you see the bread is white,

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and sometimes it's green. So you can spot the difference between them if it's rotten or not.

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Mm-hm. If a food smells funny, or off,

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or if it looks peculiar, that's a really good warning sign, isn't it?

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Well, I've brought some items along for you to smell. See if you think they're off.

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Here's the first one.

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Cheese. What do you think of that?

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-That's all right.

-Urgh!

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I don't think it's off.

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It's strong but I wouldn't say it's off.

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It's not off, but it smells really, really strong.

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Yeah, it's strong, but it's not a lot to...

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Let's try... Now, don't smell this one, OK?

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It's mouldy bread, so you don't have to smell it.

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Very mouldy, isn't it?

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If you found that in your bread bin,

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-you wouldn't want to put that in your toaster, would you?

-No,

0:21:070:21:11

you'd be mad to eat that.

0:21:110:21:13

Dark green, yellow...

0:21:140:21:17

Yellow in the bottom...

0:21:170:21:19

It's mostly green on the top.

0:21:190:21:22

Eugh!

0:21:220:21:23

It looks like a sponge you use for washing the dishes!

0:21:230:21:27

HE LAUGHS

0:21:270:21:29

Now, I've got an extra special treat -

0:21:290:21:31

I've brought you your lunch. Have a good smell of that. That's fish.

0:21:310:21:35

Urgh!

0:21:350:21:36

That's disgusting!

0:21:360:21:39

Oh! Ho, ho!

0:21:410:21:43

HE CHOKES

0:21:430:21:44

That is...

0:21:440:21:47

Eugh!

0:21:470:21:49

THEY LAUGH

0:21:490:21:52

Anyone else want an extra smell?

0:21:520:21:54

THEY LAUGH AND SHRIEK

0:21:540:21:56

The reason this smells SO bad

0:21:580:22:00

is it's loaded with bacteria

0:22:000:22:02

that have all been developing in there,

0:22:020:22:04

and they're producing toxins and gases,

0:22:040:22:07

and that really dreadful smell

0:22:070:22:10

is warning you that that's really off. You wouldn't eat this

0:22:100:22:13

in a million years, would you?

0:22:130:22:16

-If it was the last thing on earth.

-If it was the last thing on earth...

-GIGGLING

0:22:160:22:21

There is an overpowering stench inside the giant Rot Box, too,

0:22:240:22:29

as the bacteria breaks down the food

0:22:290:22:32

which has now been decaying for two days.

0:22:320:22:34

Let's take a closer look at them under the microscope.

0:22:340:22:39

This bacterium, Pseudomonas, magnified 7,000 times,

0:22:390:22:43

is the most common type of food-rotting bacteria.

0:22:430:22:48

There are as many as a trillion individual bacterial cells

0:22:480:22:53

in this sample alone.

0:22:530:22:56

We can't see bacteria without a microscope,

0:22:560:22:59

but they're absolutely everywhere.

0:22:590:23:02

They're the most common agent of decay on the planet.

0:23:020:23:06

They're the first to attack dead animals

0:23:060:23:09

because they're already living on them.

0:23:090:23:12

All creatures carry bacteria.

0:23:120:23:15

These bacteria were on our chicken when it was alive,

0:23:150:23:20

and now that it's dead,

0:23:200:23:22

they've quickly begun to decompose its flesh.

0:23:220:23:25

-Who can tell me something about bacteria?

-They're small.

-Very small.

0:23:330:23:39

-You need a microscope to see them.

-You do need a microscope.

0:23:390:23:43

In fact, here is a teaspoonful of soil.

0:23:430:23:46

How many bacteria do you think are in that teaspoonful of soil?

0:23:460:23:49

-Over a million?

-There are 40 million bacteria in that amount of soil.

0:23:490:23:54

It's hard to see them, but it's easier to see what they do,

0:23:540:23:57

and on here, I've got a film of a chicken that we put in the Rot Box.

0:23:570:24:02

Now, look at this. Watch this.

0:24:020:24:07

-THEY ALL GASP

-What's going on there?

0:24:070:24:10

-It's blowing up.

-Like a balloon.

0:24:100:24:12

It's blowing up like a balloon.

0:24:120:24:14

That was a fresh chicken, a completely fresh chicken,

0:24:140:24:17

but any piece of fresh meat has bacteria on it,

0:24:170:24:21

and because we just left that in the open, the bacteria grew and grew.

0:24:210:24:26

Some of these bacteria are really quite hazardous,

0:24:260:24:29

so if you ate uncooked meat, you'd be quite ill.

0:24:290:24:32

So, with all these bacteria around, how can you make food safe?

0:24:320:24:36

-You can refrigerate it.

-Yeah.

0:24:360:24:38

-You could cook it and then put it back in the fridge.

-Absolutely.

0:24:380:24:42

-What do organisms need to grow?

-Water!

-Water, yeah. OK.

0:24:420:24:47

So you could dry it, you could freeze it,

0:24:470:24:51

you could heat it up, if it's cooked.

0:24:510:24:54

-Would cooking a chicken make it safe for ever?

-ALL: No.

-No, it wouldn't.

0:24:540:24:59

-Because it would eventually rot, as well.

-Yeah.

0:24:590:25:03

So it's all about slowing down the bacterial growth, isn't it?

0:25:030:25:08

In the Rot Box, we had the ideal environment for growing bacteria.

0:25:080:25:12

It was hot, it was humid, and there was air,

0:25:120:25:15

so bearing that in mind, I want to set you a challenge.

0:25:150:25:18

I'm going to divide you into two teams

0:25:180:25:21

and you're going to a supermarket to find different foods

0:25:210:25:25

that have been preserved in different ways. OK?

0:25:250:25:27

-Are you up for that?

-ALL: Yes!

0:25:270:25:30

What's in that? That's good.

0:25:420:25:44

CHILDREN CHATTER

0:25:440:25:46

-So what shall we get?

-We need something sealed, tinned, boxed...

0:25:460:25:52

-I think it looks good.

-Yeah.

0:25:520:25:54

Frozen - ah, here we are!

0:25:590:26:02

Oh, cans! Yeah.

0:26:020:26:04

On the hunt for baked beans.

0:26:040:26:06

There we are. Right.

0:26:060:26:08

Done!

0:26:080:26:10

Let's start with the girls' team. What have you got?

0:26:110:26:14

-Vacuum-packed coffee.

-And that's preserved because...?

-No air.

0:26:140:26:20

There's no air, so that'll slow the bacteria down.

0:26:200:26:22

-What else have you got?

-Dried mango.

0:26:220:26:26

There's no water in it so, again,

0:26:260:26:28

that'll stop the bacteria growing. Anything else?

0:26:280:26:31

-Gammon. There's no air and it was cold. It was in the fridge.

-OK.

0:26:310:26:38

It probably has preservatives in it, as well.

0:26:380:26:41

They add preservatives to make food last longer.

0:26:410:26:44

Good work, girls. Let's see what the boys have got.

0:26:440:26:47

-We've for croutons, which we bought because they were dry.

-Absolutely.

0:26:470:26:52

Dry as a bone in there. OK. What next?

0:26:520:26:55

Olives, cos they're in water,

0:26:550:26:58

and when they're in water, we thought the bacteria would slow down

0:26:580:27:03

because we've never seen rotten olives before.

0:27:030:27:07

Water's not going to be good because that'll encourage bacterial growth.

0:27:070:27:11

It's actually olive oil in here, and it's been vacuum-packed as well,

0:27:110:27:16

so if you keep that shut, it should stay fresh - or not rot -

0:27:160:27:21

for quite a long time.

0:27:210:27:22

We got baked beans, because they're tinned

0:27:220:27:26

and it would be harder for the bacteria to go in

0:27:260:27:31

because it's tinned.

0:27:310:27:34

So, unless you open that can,

0:27:340:27:37

it'll probably stay fresh for a very long time.

0:27:370:27:39

I am amazed that nobody picked frozen food,

0:27:390:27:44

one of the commonest ways of preserving food.

0:27:440:27:47

It's so cold no bacteria will grow in there. Or, if they do,

0:27:470:27:51

it'll be very, very slow indeed.

0:27:510:27:54

All these are brilliant techniques at slowing down

0:27:540:27:57

the growth of bacteria - you exclude water, you keep it cold

0:27:570:28:01

or you exclude air - so well done, everybody.

0:28:010:28:04

We can often tell when food isn't good to eat by looking at it

0:28:080:28:13

or smelling it.

0:28:130:28:15

It's easy to see mould at work.

0:28:150:28:17

We can't see bacteria,

0:28:170:28:19

because they're tiny organisms that can only be seen using a microscope.

0:28:190:28:24

But we can see the effects of what we do,

0:28:240:28:28

and we can smell the gases they produce when they're attacking food.

0:28:280:28:32

This should warn us not to eat it.

0:28:320:28:34

Bacteria are everywhere, and are already on foods like meat and fish

0:28:340:28:38

when you buy them.

0:28:380:28:40

They are the most common agents of decay on the planet.

0:28:400:28:44

Inside this large glass box,

0:28:510:28:54

something extraordinary is happening.

0:28:540:28:58

Food is being left to rot for eight weeks

0:28:580:29:01

in our own unique laboratory.

0:29:010:29:04

This is an investigation into nature's biggest

0:29:070:29:11

and best recycler - decay.

0:29:110:29:15

And it's being done on a scale that has never been tried before.

0:29:150:29:20

I'm Dr George McGavin.

0:29:200:29:22

I'm a biologist with a particular passion for insects.

0:29:220:29:26

The Rot Box detectives - Iona, Rosie,

0:29:260:29:30

Ruaridh, Mram and Jamie -

0:29:300:29:33

are going to help me investigate

0:29:330:29:36

the amazing world of rot and decay.

0:29:360:29:40

'We'll see flies...'

0:29:440:29:46

Oh. Oh-hoo!

0:29:460:29:47

Look at this.

0:29:470:29:49

'..mould...'

0:29:490:29:51

Ah! That's incredible.

0:29:510:29:53

'..and bacteria.'

0:29:530:29:55

The bacteria have been hard at work.

0:29:570:29:59

At Rot Box detective HQ, we're discovering more about bacteria.

0:30:020:30:08

Now, who can tell me something about bacteria?

0:30:080:30:11

-There's some good bacteria and some bad bacteria.

-True.

0:30:110:30:15

-They're absolutely everywhere.

-That is completely correct.

0:30:150:30:19

I went out to the garden earlier and I collected some rainwater.

0:30:190:30:22

There are one million bacteria just in that little spoonful there.

0:30:220:30:28

-One million!

-Wow.

-In there.

0:30:280:30:32

Now, the one thing about bacteria, of course, is, as you said,

0:30:320:30:35

there's good and bad ones.

0:30:350:30:38

What would happen if a bad bacterium had got inside you?

0:30:380:30:41

-You'd get a tummy bug.

-Absolutely.

0:30:410:30:45

How do you think the bacteria get inside you?

0:30:450:30:48

If you eat something but before you ate it, you didn't wash your hands.

0:30:480:30:53

Absolutely right. That is the commonest route to get internal infections,

0:30:530:30:58

internal bacteria.

0:30:580:30:59

Now, I've got a very smart trick that will show us

0:30:590:31:03

how easy it is to transfer bacteria from person to person to person.

0:31:030:31:08

OK?

0:31:080:31:09

Now, we can't see bacteria on our skin without very special equipment,

0:31:110:31:15

but I can show you how they spread around.

0:31:150:31:18

'I'm going to show the team how easy it is to spread bacteria

0:31:180:31:23

'by using this special cream that glows under ultraviolet light.'

0:31:230:31:28

You can't see it there, yeah? OK?

0:31:280:31:32

-But if I now put this under my hands, you can see...

-ALL: Ohhh!

0:31:320:31:36

..it's everywhere, OK?

0:31:370:31:41

Now, hold your hands up, Iona. Clean? In the ultraviolet. Other side.

0:31:410:31:44

Completely clean.

0:31:440:31:46

Now, if I shake your hand...

0:31:460:31:48

Hello, nice to see you! And now you put your hand under the there.

0:31:480:31:52

ALL LAUGH

0:31:520:31:53

Whoa! Now, if you shake hands with Ruaridh...

0:31:530:31:56

Hello! Shake hands. And underneath there - let's see.

0:31:590:32:02

Ew! Yes, it's spread, from me to you to you, right?

0:32:020:32:09

Very, very easy.

0:32:090:32:12

Now, imagine this was bacteria. OK?

0:32:120:32:15

I'm going to squidge it in your hands, OK, and rub that all in.

0:32:150:32:20

'Some bacteria can cause disease and make us feel unwell.

0:32:200:32:24

'You might know them as germs.

0:32:240:32:26

'They can get onto my hands when we sneeze or cough into them, or when we use the toilet.

0:32:260:32:30

'That's why it's important to wash your hands properly.

0:32:300:32:34

'I'm testing how well Jamie and Rosie wash their hands.'

0:32:340:32:37

Now, let's just check under the ultraviolet light,

0:32:370:32:41

see how glowing your hands are.

0:32:410:32:43

Ooh, yes!

0:32:430:32:45

Come on, Jamie. Squidge round. Oh, yes! Oh, yeah.

0:32:450:32:50

Go wash your hands.

0:32:500:32:52

Let's see how well they do.

0:32:520:32:55

-Ah-ha! Right, are your hands washed?

-Yes.

-Let me inspect them.

0:32:570:33:01

Do the old test.

0:33:010:33:02

Oh, yes, now if I was a parent, I'd say, "That's very good.

0:33:020:33:06

"Very good. Very clean." But is it?

0:33:060:33:08

Rosie, stick your hands under the ultraviolet.

0:33:080:33:11

-Oh-hoo-hoo! Eugh!

-ALL: Eugh!

0:33:110:33:13

Not so good.

0:33:130:33:14

It's all on your fingernail. It's all over your thumb.

0:33:140:33:18

Oh, yes, not so clean, but not bad. OK?

0:33:180:33:21

Jamie, stick your hand in there, son.

0:33:210:33:23

Let's see what we've got on yours.

0:33:230:33:25

ALL: Eugh!

0:33:250:33:28

Oh, yeah. I think Rosie won that one. Yeah, definitely, yeah.

0:33:280:33:33

It's on all your fingernails,

0:33:330:33:35

over the front and back of your hand, in the creases of your thumbs and fingers.

0:33:350:33:39

Not good enough.

0:33:390:33:41

So you see how you think you've washed your hands carefully enough,

0:33:410:33:46

but actually to wash your hands really carefully and properly to remove bacteria

0:33:460:33:50

it's quite hard.

0:33:500:33:51

The correct way to wash your hands, of course, using soap and hot water

0:33:510:33:56

is to put the soap there, rub, rub, rub, right?

0:33:560:33:59

Both sides and then interlock your fingers like this

0:33:590:34:02

and then do the backs of your fingers like that,

0:34:020:34:06

then you do your thumbs, yes?

0:34:060:34:07

And then your thumbs like that, OK?

0:34:070:34:10

And then the back of your hands like that.

0:34:100:34:13

And then rinse it all off, OK?

0:34:130:34:15

So it's actually quite hard work.

0:34:150:34:18

Bacteria are the one thing

0:34:180:34:21

that we didn't have to put inside the box because they're already there.

0:34:210:34:25

They're everywhere -

0:34:250:34:27

tiny living things, or micro-organisms, that you can't see without a microscope.

0:34:270:34:34

In the Rot Box, we have an incredible microscope

0:34:340:34:38

that magnifies the bacteria a breathtaking 7,000 times.

0:34:380:34:42

This allows us to have a much more detailed look.

0:34:420:34:46

With enough food and water,

0:34:460:34:49

the numbers of bacteria can increase alarmingly fast.

0:34:490:34:53

They increase by dividing into two every 30 minutes,

0:34:530:34:57

so after just 24 hours,

0:34:570:35:00

one bacterium becomes just over 281 billion bacteria.

0:35:000:35:07

They make up the largest number of living organisms on the planet.

0:35:070:35:13

There are trillions and trillions and trillions of micro-organisms around the earth.

0:35:130:35:19

But they're not all harmful, some of them help us.

0:35:190:35:23

Importantly, bacteria live in our gut, helping us to digest our food.

0:35:230:35:29

Now there are bacteria all over us obviously,

0:35:320:35:35

but there's also lots of bacteria inside us.

0:35:350:35:37

-Where do you think you could find lots of bacteria?

-In your stomach.

-Yeah, lots of bacteria.

0:35:370:35:44

-Up your nose.

-Yes, lots of bacteria there.

0:35:440:35:46

-In your ears.

-In your ears. Yes. Anywhere else?

0:35:460:35:50

-In your mouth.

-Particularly in your mouth,

0:35:500:35:52

so lots of bacteria in there, some are good, some are bad.

0:35:520:35:56

What I want to show you is how important it is to brush your teeth.

0:35:560:36:01

I'm sending Iona and Mram off to brush their teeth so I can demonstrate

0:36:010:36:05

how important it is to do it properly.

0:36:050:36:09

-Have you brushed them properly?

-Yes.

-Yes.

0:36:120:36:14

Well, I've got here little special tablets called disclosing tablets

0:36:140:36:18

and you can have one each, right?

0:36:180:36:21

It will show if you've really brushed your teeth properly,

0:36:210:36:26

so what I want you do to is...

0:36:260:36:28

in your mouth, roll it around your tongue

0:36:280:36:30

and get all the liquid over your teeth and gums,

0:36:300:36:33

do not swallow it,

0:36:330:36:34

and then, once you've done that, go to the kitchen

0:36:340:36:36

and spit it out and rinse your mouth out with fresh water

0:36:360:36:40

and then come back.

0:36:400:36:41

CHILDREN GIGGLE

0:36:420:36:43

Now what this does is,

0:36:450:36:46

the red dye sticks to the plaque.

0:36:460:36:49

'Plaque is a sticky film containing bacteria

0:36:490:36:52

'that can build up on your teeth.

0:36:520:36:54

'The bacteria love to feed on sugar and when they feed,

0:36:540:36:57

'they make acid which can rot your teeth.'

0:36:570:37:00

It's very important to brush all that plaque off,

0:37:000:37:03

that plaque bacteria off,

0:37:030:37:05

and the red tablets show where the plaque is.

0:37:050:37:08

Now you've brushed your teeth properly. Let's just see.

0:37:080:37:12

You've got a little bit of plaque just on the bottom of that one.

0:37:120:37:16

Yes, that's not too bad at all.

0:37:170:37:21

Let me see.

0:37:210:37:22

Open up.

0:37:230:37:25

Now there's some plaque on the edge of that tooth there,

0:37:250:37:28

some plaque along the edge of that side.

0:37:280:37:30

Now the ones who haven't brushed their teeth, right? Oh!

0:37:320:37:35

Oh-h!

0:37:350:37:37

Let's see yours.

0:37:370:37:39

Go, "Nnnnyah!"

0:37:390:37:40

Yeah. Ruaridh, open up. Oh!

0:37:420:37:47

I think you just had it on your tongue.

0:37:470:37:49

You didn't roll it around your teeth.

0:37:490:37:51

OK, that's quite clear to me that the two who've brushed their teeth

0:37:510:37:57

have done quite a good job and you've removed most of the plaque.

0:37:570:38:01

I'm impressed with you two.

0:38:010:38:03

Bacteria are micro-organisms, tiny single-celled creatures

0:38:080:38:12

that can't be seen without a microscope.

0:38:120:38:15

They're absolutely everywhere

0:38:170:38:19

and can multiply in numbers incredibly quickly.

0:38:190:38:22

As a result, there are trillions and trillions and trillions of them on earth.

0:38:220:38:28

Not all bacteria are harmful, some can be helpful too.

0:38:280:38:33

They're very easily spread,

0:38:330:38:35

so it's important to wash hands and brush teeth thoroughly.

0:38:350:38:38

This will help to stop the spread of harmful bacteria

0:38:380:38:42

or germs.

0:38:420:38:44

Inside this large glass box,

0:38:550:38:58

something extraordinary is happening.

0:38:580:39:01

Food is being left to rot for eight weeks in our own unique laboratory.

0:39:010:39:08

This is an investigation

0:39:110:39:12

into nature's biggest and best recycler - decay.

0:39:120:39:18

And it's being done on a scale that has never been tried before.

0:39:180:39:23

I'm Dr George McGavin.

0:39:230:39:26

I'm a biologist with a particular passion for insects.

0:39:260:39:30

The Rot Box detectives, Iona, Rosie,

0:39:300:39:34

Ruaridh, Mram and Jamie

0:39:340:39:38

are going to help me investigate the amazing world of rot and decay.

0:39:380:39:43

'There's mould...'

0:39:470:39:49

The mould has just covered that entire box.

0:39:490:39:53

'..bacteria...'

0:39:530:39:54

-Where you can see those glowing bits...

-Yeah.

0:39:540:39:57

..that's bacteria.

0:39:570:39:59

'..and flies.'

0:39:590:40:00

It's pretty unpleasant, I've got to say.

0:40:010:40:03

'It has taken eight months to build this giant Rot Box

0:40:070:40:10

'and now conditions are perfect inside.

0:40:100:40:14

'It's warm, there's water, air and plenty of food -

0:40:150:40:18

'all the things decay loves to feast and grow on.

0:40:180:40:24

'In the real world, female flies find the stench of rot irresistible

0:40:240:40:28

'and will be attracted to it instantly,

0:40:280:40:31

'as they find it the ideal place to lay their eggs,

0:40:310:40:35

'but because our Rot Box is sealed, no smell is escaping,

0:40:350:40:39

'so we need to put the flies into the box.'

0:40:390:40:42

And there they go.

0:40:420:40:44

Well, that's it. We're up and running

0:40:440:40:46

and it's time to leave all this to the agents of decay.

0:40:460:40:50

Back at Rot Box Detective HQ,

0:40:550:40:57

we wanted to investigate flies in more detail.

0:40:570:41:01

An adult fly can live up to five days,

0:41:010:41:04

but in such a short life, this tiny creature is incredibly busy.

0:41:040:41:09

This is a fly actually laying an egg. Now look at that.

0:41:090:41:13

See? The female's got this long bit at the back of the abdomen

0:41:130:41:16

through which the eggs pass,

0:41:160:41:17

so she's actually laying eggs there on some meat.

0:41:170:41:21

ALL: Wow!

0:41:210:41:23

-Oh, that's a fly!

-Oh, right!

0:41:230:41:27

Now if we go to the maggot,

0:41:270:41:29

when those eggs hatch and the little fly larvae,

0:41:290:41:32

which are called maggots, hatch out,

0:41:320:41:34

they've got little sharp hooks at the head end

0:41:340:41:36

with which they tear the meat. Look at that.

0:41:360:41:39

-Look. See?

-That's horrible.

0:41:390:41:41

And they just rip through the meat.

0:41:410:41:44

Now the great thing about fly maggots is that they can breathe through special holes

0:41:440:41:48

at their rear end called spiracles,

0:41:480:41:51

so we breathe through our mouths, fly larvae haven't got that -

0:41:510:41:54

they breathe through a system of tubes,

0:41:540:41:57

so it can feed and breathe at the same time.

0:41:570:41:59

And the last film is a fly after it's fully-grown,

0:41:590:42:03

after the maggot's eaten all it can eat,

0:42:030:42:05

it then becomes a pupae and it stays in there

0:42:050:42:09

and it emerges as an adult fly and here is a film.

0:42:090:42:12

Look at this. Wow! here is a fly actually emerging,

0:42:120:42:16

and after it's pushed itself out, it dries one wing,

0:42:160:42:19

and then it dries the other wing

0:42:190:42:22

and then it flies off.

0:42:220:42:23

Cool!

0:42:230:42:25

Oh, look, now it's flying.

0:42:250:42:27

Fantastic.

0:42:270:42:29

There you go.

0:42:290:42:30

We're making flytraps

0:42:340:42:36

to see how many flies will smell our rotting fish,

0:42:360:42:38

so that we can have a closer look at them in action.

0:42:380:42:42

That's the trap made. What we have to do now to attract the flies is to put in the bait.

0:42:510:42:57

Now, do you want a head or a tail?

0:42:570:42:59

-A head.

-Head. All right. Hold that.

0:42:590:43:01

We should have one head left. Oh, there it is.

0:43:010:43:05

-ALL: Eugh!

-Eugh!

0:43:050:43:06

Lovely fishy bait. Smelly, smelly. And then you put that in.

0:43:060:43:09

Stick it in there. So there we are.

0:43:090:43:12

Now, how do you think the trap works?

0:43:120:43:16

The fly goes in that hole and then it gets stuck and then it can't fly out.

0:43:160:43:20

-Yeah, it's like a creel or a lobster pot.

-Can't it go out there?

0:43:200:43:25

Some flies could fly out again, but flies are not terribly bright,

0:43:250:43:29

and after they're in there, they tend to fly up,

0:43:290:43:32

so they don't find the hole very easily,

0:43:320:43:36

so although some of them will escape, not many of them escape.

0:43:360:43:39

And there is your completed flytrap.

0:43:390:43:42

-Awesome.

-Now where would be the best place to hang them up?

0:43:420:43:46

A bright place, somewhere really warm, so it attracts more flies

0:43:460:43:50

-and the fish gets more rotten.

-Absolutely.

0:43:500:43:53

I'll bet you anything, within 30 seconds, there'll be flies in there.

0:43:530:43:57

Oh, look, there's a fly in it already.

0:43:570:43:59

Oh, see how efficient it is.

0:43:590:44:01

Right, let's go.

0:44:010:44:04

Now why do you think the adult flies are attracted to the dead fish?

0:44:070:44:11

Because they want to leave an egg there?

0:44:110:44:16

Absolutely. That's where they lay their eggs.

0:44:160:44:18

Now adult flies don't live very long -

0:44:180:44:20

they only live about five or six days,

0:44:200:44:23

so when they're adult,

0:44:230:44:24

the only job they have is to mate and to lay their eggs.

0:44:240:44:27

I'm going to hang my trap up on this bolt over here,

0:44:270:44:31

-and then we'll hang yours up on those trees, OK?

-Mm-hm.

0:44:310:44:34

'A few hours later,

0:44:450:44:47

'and we're back at the traps to see if they're a success.'

0:44:470:44:50

Right, let's see who's caught the most flies.

0:44:500:44:53

-Whose trap is this one?

-Me and Rosie.

0:44:530:44:55

Right, well, you've got four flies on the inside,

0:44:550:44:59

quite a few on the outside and you've got lots of eggs on the head,

0:44:590:45:03

so that's really good.

0:45:030:45:04

Look, we nearly got one!

0:45:040:45:06

Let me see. Oh, you have got small ones on the outside.

0:45:060:45:09

You've got one fly at the back there

0:45:090:45:12

and no eggs.

0:45:120:45:14

Mmm?

0:45:140:45:16

And now, my trap...

0:45:170:45:19

..ooh, look at that.

0:45:200:45:22

-ALL: Oh-h!

-There's at least one, two, three, four, five, six, seven flies in there -

0:45:220:45:26

three species and lots of eggs. Look at that.

0:45:260:45:29

You can see all the eggs over the mouth

0:45:290:45:32

and in the mouth and on the head end, see? It could all change,

0:45:320:45:36

-because there might be more flies in your traps tomorrow.

-Yeah.

0:45:360:45:39

After five weeks, the Rot Box has begun to look like a giant flytrap.

0:45:430:45:49

There are now up to 10,000 flies trapped inside.

0:45:490:45:52

Outside in the real world, these flies would have escaped

0:45:550:45:59

out of a open window, but because the box is sealed,

0:45:590:46:02

they've got nowhere to go and food is running out fast.

0:46:020:46:07

I'm worried this huge number of flies will upset the balance of life in the box,

0:46:080:46:13

so I've decided to go in and take control.

0:46:130:46:17

Well, there are just now simply too many flies in here.

0:46:230:46:27

It's becoming quite unpleasant,

0:46:270:46:29

and it's causing a problem,

0:46:290:46:30

because of the flyspeck, that's their excrement,

0:46:300:46:33

which they leave on the surfaces inside the glass everywhere,

0:46:330:46:36

so it's time I tried to reduce them a little bit...

0:46:360:46:40

..manually.

0:46:410:46:43

The trouble is, they're flying quite low

0:46:430:46:47

and they're sitting on surfaces - it's actually very hard to get them.

0:46:470:46:51

It's no wonder flies are so hard to capture.

0:46:570:46:59

Their compound eyes give them all-round vision,

0:46:590:47:02

so they can respond to movement in a fraction of a second.

0:47:020:47:07

I'm never going to win this fly hunt.

0:47:090:47:11

'The team and I are taking the fly hunt outside.'

0:47:160:47:19

Right, well, we've been quite lucky with the rain.

0:47:190:47:22

Yep.

0:47:220:47:23

Oh, look at this. Look what I've found.

0:47:240:47:27

Look.

0:47:270:47:28

-Oh, wow!

-Look at that.

-Aw-w!

0:47:300:47:34

Who knows what that is?

0:47:340:47:36

-A pheasant.

-Yeah, it's a female pheasant

0:47:360:47:38

and I think it's probably been hit by a car, actually.

0:47:380:47:40

In the real world, everything dies at some point,

0:47:400:47:44

and when they do, bacteria start to act on them, breaking it down.

0:47:440:47:49

They produce smells, bad odours which attract organisms,

0:47:490:47:52

and if you remember back to your flytraps,

0:47:520:47:55

the flies were attracted to the decaying fish pretty quickly,

0:47:550:47:58

and the same thing will happen here.

0:47:580:48:00

Now what would happen if we didn't have flies laying their eggs in it,

0:48:000:48:04

and maggots eating it and other animals taking it away?

0:48:040:48:07

-What would happen?

-There'd be, like, loads of dead animals everywhere

0:48:070:48:10

-and it would smell.

-Exactly.

0:48:100:48:12

Flies and other things that recycle dead animals

0:48:120:48:16

really perform a fantastic job for us.

0:48:160:48:19

Flies, particularly, are one of the most important recycling animals.

0:48:190:48:23

Right, let's go.

0:48:230:48:24

Back at the Rot Box, the cycle of life continues.

0:48:320:48:35

Female flies are attracted to the rotting food,

0:48:360:48:39

laying up to 300 eggs at a time.

0:48:390:48:42

The eggs hatch into larvae called maggots.

0:48:430:48:46

Maggots are amazing feeders. They use sharp hooks to eat

0:48:460:48:50

and breathe through air holes called spiracles in their rear end.

0:48:500:48:55

The maggots then become pupae

0:48:550:48:57

from which young flies emerge and the whole cycle will begin again.

0:48:570:49:02

So even though flies spread bacteria and mould

0:49:020:49:05

by landing on fresh food,

0:49:050:49:06

they have a very important job as recyclers.

0:49:060:49:10

Inside this large glass box

0:49:170:49:20

something extraordinary is happening.

0:49:200:49:23

Food is being left to rot for eight weeks in our own unique laboratory.

0:49:230:49:30

This is an investigation into nature's biggest and best recycler...

0:49:330:49:38

..decay,

0:49:390:49:40

and it's being done on a scale

0:49:400:49:42

that has never been tried before.

0:49:420:49:47

I'm Dr George McGavin.

0:49:470:49:48

I'm a biologist with a particular passion for insects.

0:49:480:49:52

The Rot Box detectives, Iona, Rosie,

0:49:520:49:56

Ruaridh, Mram and Jamie

0:49:560:50:00

are going to help me investigate the amazing world of rot and decay.

0:50:000:50:06

'There's mound...'

0:50:080:50:10

The melon's just incredible. It's really been hammered. Look at that.

0:50:100:50:14

'..flies...'

0:50:140:50:15

The number of flies has absolutely skyrocketed.

0:50:150:50:19

'..and bacteria.'

0:50:190:50:20

As well as food, there's a compost heap in the Rot Box,

0:50:280:50:31

which includes vegetable waste and leaves.

0:50:310:50:34

This is a great place to see decomposition in action.

0:50:360:50:41

We've been adding green material to the top,

0:50:410:50:44

but if we clear the top layers down, what's been happening in here

0:50:440:50:47

is lots and lots of woodlice, worms beetles have been working away

0:50:470:50:52

at the green material, breaking it down,

0:50:520:50:55

decomposing it into smaller material,

0:50:550:50:57

smaller particles,

0:50:570:50:59

and that is then available for use

0:50:590:51:01

by the billions of bacteria and fungi which are also in here.

0:51:010:51:05

We'll be back to have a much more detailed look at these later on.

0:51:050:51:10

Back at Rot Box Detective HQ,

0:51:150:51:17

we are collecting leaves for our compost bin.

0:51:170:51:20

It's the best place to see natural recycling at work.

0:51:200:51:25

Right, let's come over to the compost bin.

0:51:290:51:34

Let me take that.

0:51:340:51:35

-Now do any of you do recycling?

-Yeah, I do.

0:51:350:51:40

Glass, paper and cardboard.

0:51:400:51:42

-OK.

-We recycle the garbage in our garden.

-Right.

0:51:420:51:45

-Oh, you do? So you've got a brown bin, have you?

-Yeah.

0:51:450:51:50

I've got a brown bin so I put, like, hedge cuttings and grass cuttings in it.

0:51:500:51:55

-So all the waste from the garden ends up in here?

-Yeah.

-Yeah.

0:51:550:51:58

That's what we're going to with the leaves we've raked up,

0:51:580:52:01

but before we empty it in, put your hand in there, tell me what you feel.

0:52:010:52:06

-Leaves.

-Nothing.

-Oh, it's warm.

0:52:060:52:08

It's warm!

0:52:080:52:09

-Oh, yeah.

-Wow!

0:52:090:52:11

Well, that's the bacteria breaking the stuff down.

0:52:110:52:14

-Right, empty the leaves in.

-Will there be enough room?

-Oh, yeah.

0:52:140:52:18

-Oh, yeah.

-There we are.

-Sorry.

-Right.

0:52:180:52:23

Who knows where this goes?

0:52:230:52:24

Once you've filled up your brown bin, where does it go?

0:52:240:52:28

-Bin lorry.

-Ah, well, I'm going to show you.

0:52:280:52:31

The leaves that we collected in the garden, we raked them up into the brown bin.

0:52:470:52:52

The brown bin gets picked up by the truck,

0:52:520:52:54

and the trucks all come here and there's one arriving now.

0:52:540:52:58

They open the back, all the green material gets pushed out,

0:52:580:53:01

and then a scoop comes and takes it to a shredder.

0:53:010:53:05

That's where the whole process begins.

0:53:050:53:07

It falls through these two huge rotating bars.

0:53:070:53:12

It grinds it all up

0:53:120:53:14

and it spits it out the bottom onto a bed

0:53:140:53:16

and then it gets carried out there into a pile

0:53:160:53:19

and the reason they do that is to break up

0:53:190:53:21

all that material into smaller bits,

0:53:210:53:24

so that it has a larger surface area,

0:53:240:53:27

so the bacteria can get to work on it.

0:53:270:53:28

Right, now, this... is where it all comes.

0:53:410:53:44

So, once it's been through the shredder,

0:53:440:53:47

it gets piled up in these long rows.

0:53:470:53:49

Now, the reason they don't pile it in one great pile

0:53:490:53:52

is if they had it in one huge pile, it would go all slimy,

0:53:520:53:56

there'd be no oxygen in the middle.

0:53:560:53:57

It would go all horrible.

0:53:570:53:59

So they have it in these rows so they get lots of air in there

0:53:590:54:02

and the air helps the bacteria and the decomposition.

0:54:020:54:04

And what happens next is they put this through a screen or a sieve,

0:54:040:54:09

it's like a giant sieve, and they take out all the big bits.

0:54:090:54:13

So all you're left with is fine compost.

0:54:130:54:16

-How hot do you think it is in there?

-20 degrees?

-No.

0:54:160:54:19

-40?

-No. Hotter than that.

0:54:190:54:22

-50 degrees?

-Hotter than that.

0:54:220:54:24

-85 degrees.

-That's a pretty good estimate. Let's see how hot it is.

0:54:240:54:29

'I'm using a thermal probe to measure the heat inside the pile.'

0:54:290:54:33

Let's see exactly how hot it is.

0:54:340:54:36

47, 49...50...

0:54:420:54:45

Going up!

0:54:460:54:48

-Will it make 60?

-Yes, it will.

0:54:490:54:51

-It will, it will!

-59.9...

0:54:510:54:55

60!

0:54:550:54:56

60 and rising. Now, the reason it gets really hot in here

0:54:560:54:59

is because there's billions of bacteria in here,

0:54:590:55:02

breaking all the material down

0:55:020:55:04

and as they break it down, they produce large amounts of heat.

0:55:040:55:08

What's the highest?

0:55:080:55:09

Some of these piles have even had fires in them

0:55:090:55:13

cos it's just so hot. That's the power of bacteria.

0:55:130:55:15

Now, once they've taken out all the big bits,

0:55:190:55:21

all the big bits of wood and roots and stuff,

0:55:210:55:23

the end result of all that recycling

0:55:230:55:25

is this beautiful, beautiful compost.

0:55:250:55:28

And that goes straight on your garden.

0:55:280:55:30

Now, we've speeded it up by having it broken down into smaller bits,

0:55:300:55:34

but recycling is happening all the time, all around us.

0:55:340:55:38

Back in the giant Rot Box, we can take a much closer look

0:55:420:55:45

at how recycling is happening in the compost heap.

0:55:450:55:48

As all gardeners know, compost turns dead plants

0:55:540:55:57

into a form of nutrient that new plants can use.

0:55:570:56:01

On the surface, animals like snails, slugs

0:56:040:56:06

and worms begin the process by eating the remains of plants,

0:56:060:56:10

helping to break them into smaller pieces.

0:56:100:56:13

Other small animals, like these mites,

0:56:160:56:18

feed on the waste products these creatures leave behind.

0:56:180:56:22

This process continues down through the compost,

0:56:240:56:27

with ever-smaller organisms reducing the plant waste

0:56:270:56:30

to ever-smaller pieces, until tiny micro-fauna

0:56:300:56:35

and bacteria are able to break down the very cells of the plants.

0:56:350:56:39

A teaspoon of soil contains four billion micro-organisms.

0:56:410:56:46

They finally release the goodness back into the soil

0:56:460:56:49

so that new organic life can grow.

0:56:490:56:51

Composting is happening all around us in the natural world.

0:56:570:57:02

I'm taking the Rot Box Detectives out to see if we can find some.

0:57:020:57:06

Now, over here...is what I like to see. A bit of decaying wood.

0:57:060:57:12

Now, look at this, this is fantastic.

0:57:130:57:16

Now, this is a brilliant habitat for all kinds of stuff.

0:57:160:57:20

This was once a piece of a tree.

0:57:200:57:22

Obviously, it's fallen off

0:57:220:57:24

and the whole of the wood is being eaten away,

0:57:240:57:27

transformed into just...

0:57:270:57:29

Look at that. It's all breaking down.

0:57:290:57:31

The thing I love about decaying wood is it has a wonderful smell.

0:57:330:57:37

Absolutely gorgeous.

0:57:410:57:43

The whole of the wood is being eaten away,

0:57:450:57:48

transformed into just... Look at that.

0:57:480:57:50

It's exactly the same process that we saw earlier.

0:57:500:57:53

It's recycling on a grand scale.

0:57:530:57:55

Composting is nature's wonderful way of recycling.

0:58:010:58:05

Plant and vegetable matter are gradually broken down.

0:58:050:58:09

First, by larger organisms like snails, slugs, worms

0:58:100:58:13

and woodlice, then by ever-smaller micro-organisms and bacteria.

0:58:130:58:19

This process can be speeded up by breaking down the organic matter

0:58:200:58:24

into small pieces, using machines.

0:58:240:58:28

The end result is beautiful compost,

0:58:280:58:30

full of goodness, ready to feed more plants

0:58:300:58:34

so that the whole process of life and growth can begin again.

0:58:340:58:38

Subtitles by Red Bee Media Ltd

0:58:580:59:01

E-mail subtitling@bbc.co.uk

0:59:010:59:04

A special spin off programme of the BBC Four programme After Life for learners aged 7 - 11 years.

A team of young science detectives investigate rot and decay through a series of experiments and activities, assisted by Dr George McGavin. The team find out not just about the bacteria all around us, but the bacteria on our skin, in our mouths and in our stomachs. They look at the life cycle of flies and how they play an important part in the natural process of recycling and composting. They even make their very own rot boxes which they fill with food and leave for six weeks.

Featuring microscopic and time-lapse footage of rot from the original After Life programme, Rot Box Detectives highlights the beauty of decay in the natural world.