Do Bacteria Grow on Bars of Soap?

Cells lining blood vessels in the brain can grab clots and other obstructions and dump them outside the vessel to restore blood flow, US researchers have found.

In a paper in Nature, Northwestern University scientist Carson Lam and his colleagues use a clever imaging technique (called two photon imaging) to watch what happens when fluorescently-labelled blobs of cholesterol are released into the blood vessels supplying the brains of mice.  To their surprise, whenever the glowing balls of fat lodged in a small blood vessel, blocking it, within a few days it had been cleared and was sitting outside the blood vessel, almost as though a snow-plough had pushed it out of the road like a snow drift.

A closer look at how the process was taking place revealed that the endothelial cells, which form the linings of blood vessels, were orchestrating a sequence of events never seen before.

The cells were putting out thin extensions of their membranes and completely enveloping the obstruction before opening up a channel between them and their neighbours and ejecting the material from the inside of the vessel.  Interestingly, when the team compared this behaviour in young versus older mice, they found that it was much less efficient with increasing age and there was considerably more brain injury as a result in these older animals.

This might help to explain in part, say the researchers, why humans succumb to deteriorating brain function as we age.  At the same time it might also account for the observation that diseases like diabetes and high blood pressure - which can make the walls of small vessels much thicker - tend to increase the risk of stroke and dementia, perhaps because blood vessels damaged in this way find it more difficult to unblock themselves, leading to neuronal loss.

Clearly it's early days yet, but getting to the bottom of this observation could open up new avenues in brain protection and repair.

A new fossil study reveals that the ancient ancestors of octopuses, squid, and cuttlefish have been swimming through the oceans for at least 30 million years longer than previously thought.

Originally only a single fossil of a mysterious creature named Nectocaris pteryx was found in the famous Burgess Shale deposits in Canada. And for a long time researchers were stumped as to what kind of animal it was.

Now, writing in the journal Nature, Martin Smith from the University of Toronto leads a study that reveals a series of key characteristics that tie Nectocaris to the group of molluscs, including octopuses and squid, known as cephalopods.

Over 90 new specimens have been found of the tiny creatures that were between two to four centimetres long. They had large, stalked eyes and a long pair of grasping tentacles, which they probably used to hunt for and eat prey. The researchers think they used jet propulsion to push themselves along by forcing water through a nozzle-like funnel, like many modern cephalopods do today.

Nectocaris evolved around 500 million years ago, not long after the so-called Cambrian explosion when a plethora of complex, multicellular life emerged over a short period of time setting the stage for the evolution of many groups of animals still around today.This study changes the commonly held view of the cephalopods not only because it pushes back the date when they first evolved, but it also offers insight into how they evolved into other modern and extinct forms. Nectocaris had no hard shell and it swam actively around the ocean, which goes against theories that cephalopods first evolved from ancient, bottom-dwelling molluscs with heavy, hard shells which later evolved into the floating devices found inside other cephalopods, the extinct ammonites and living chambered nautilus.

Many questions still remain about Nectocaris and the beginnings of the cephalopods but we now have a much clearer picture of what was going on 500 million years ago. We even know how some of these Nectocaris creatures died: their gills are choked in fine deposits, telling us they were probably buried in an underwater mudslide.

We put this question to Dominic Ford from Naked Astronomy.

Dominic - Well, it's of course very hard to know what life there is out there. People have looked for radio radiation from other civilisations using the Arecibo telescope in America and there are future telescopes that we'd hope to pick up radiation from aircraft radar and television transmitters on other planets. So far, they haven't picked up anything in the closest thousand, tens of thousands of stars around the earth. So we probably think there's not much life immediately close to the Earth but it's very hard to know what is out there.

Chris - A few years ago, in fact it was five years ago, I was in Washington DC at the AAAS conference and there was number of people at the conference talking about things like the SETI program looking for life. Some of the world's leading space scientists were right there and so we had them on a radio program, and I went along the table and said, "I'd like you all to guess or give any estimates as to the likelihood of us finding alien life within the next 50 years." Just out of interest, where would you put that number?

Dominic - I think there were a number of very interesting space missions coming up in the next 10 or 15 years which have the potential to see earth-like planets surround other stars. If we see those planets and we manage to see the light from those planets, we can take a spectrum of them and we can see what molecules are in their atmospheres. And if we start to see organic molecules in those atmospheres, we will know there is almost certainly life on those planets. It may not intelligent. It's very hard to tell whether it's intelligent, but I think there is a lot of potential to see microbial life in the next 10, 15 years. Chris - Whether or not you'd call life on earth necessarily intelligent is also open to debate. It depends where you look, I think. Dominic, thank you very much.

Chris - The answer is actually, yes, they can - because soap isn't actually very toxic for bacteria. The reason that washing your hands with soap and water works so well to decontaminate them is actually the physical decontamination. When you rub your hands together, the soap helps to prise away various oils and other layers from the skin that the bacteria are clinging to and it therefore detaches the bacteria. It's not actually being necessarily antibacterial. Now some soaps will kill bacteria. The majority don't because the bacteria have got quite a tough cell wall around them, so they're resistant, but it's the physical washing that gets rid of them.

One interesting thing though, when we've had lots of outbreaks of winter vomiting disease, the norovirus, you see lots and lots of these alcohol dispensers springing up all over the place, saying, "Clean your hands. This will help to stem outbreaks of norovirus." Actually, norovirus doesn't have around its outside an oily bag which can be attacked by alcohol. It's a very tough little protein husk that the virus is made of and as a result, the virus is completely immune to alcohol hand wipes, and therefore, all you're doing when you're using alcohol is you're producing a pure culture of norovirus on your hands. Soap and water on the other hand does work. So the best thing to do, is always wash your hands. Helen.

Helen - Well that is rather lovely, but I just wanted to ask. I've always wondered. If you go to a public loo, there's a nasty bit of soap sitting on the side and you think, "Yuck!" Is it better to use that soap if it's covered in bacteria and wash your hands and rub off your own bacteria, or should you leave it alone? What do you think?

Chris - This is a bugbear of mine actually because when you go to public conveniences, the first thing you have to do to get into them is open the door of course, and the door always opens inwards. You can push the door open which means you don't have to touch any part of it. But when you're coming out again, you have to touch the handle on the door of the loo then you got to touch all over the taps, and then you've got to touch the door handle to open it and pull it inwards again.

Now okay, lots of people will be good in the toilet. They won't make a mess, but they will also wash their hands diligently afterwards. You then go out, leaving the toilet with clean hands, but you touch the door handle that the one in a million people who haven't washed their hands has just touched and decorated with a nice culture of bacteria, of faecal origin probably but also other things are possible. It's now on your hands - which were nice and clean, so there are no other bugs there to compete with them, so now you've got a nice pure culture of pathogens all over your hands.

Why are the doors are not organised so that you can push the door open on the way out or have some kind of automatic door? More lavatories these days are getting themselves organised so that you sort of go around almost like a maze to get out. But it means you don't have to physically open external doors to get out and touch surfaces because that's how these bacteria spread - it's touching surfaces. So to answer your question, you will pick up bugs when you touch surfaces including the soap dispenser and this is why in many places where medicine is done, doctors' surgeries, nurses' rooms and so on, you'll see that the taps have these long wings on them. This is so that you can actually close them off with your elbows, rather than actually having to physically touch them with the thing you've just washed. So sorry Helen, despite your best ministrations to your hands, you're probably actually picking up bugs by using that grotty bit of soap, I'm sorry to say.

Helen - I'll just have to keep my elbows clean by the sound of it.

We asked Dominic Ford from Naked Astronomy.

Dominic - Yes, it certainly would be. What's important is whether the average density of the sphere plus whatever is inside it is greater or less than the density of the water that it will be floating in. So for example, a ship floats because although a ship is made of steel and that's very heavy, it's got air in there as well and the air is much less dense than the water it's floating in, so a ship as a whole floats.

Now, if you take a sphere, the metal outside of the sphere will be much heavier than the water, but because it hasn't got anything in it, that doesn't contribute to the density. So its average density be quite low. So it will float. It will actually float better than if you filled it with hydrogen or helium which, although they are lighter than air, they still have some mass to them, more than the mass of the vacuum which is nothing at all.

Chris - Indeed. It's a good party question that, isn't it? Which is going to float more, a sealed barrel full of air, a sealed barrel full of hydrogen, or a barrel with a vacuum? Most people will go for the hydrogen, but, actually, it's the vacuum that floats the best!

Dominic - Yes, of course. You don't see barrels "filled" with vacuums very often, because it's so hard to suck air out of a barrel!

Chris -  Well now, it's time to join Meera Senthilingam who's been off enjoying the sunshine this week at the Royal Horticultural Society's Chelsea Flower Show and she's been finding out how to save the rainforest and entice lots of wildlife into her garden...

Meera -   Here in the UK, it's been brightening up.  It's a lot hotter, which means that all of us are out and about, getting our gardens ready for the barbecue season.  Now the highlight of any horticulturists calendar is the Royal Horticultural Society's Chelsea Flower Show.  One particular concern being addressed is the destruction of our rainforest.  So I'm now in a beautiful stand, sitting in a lovely wooden hut with John Burton who's the CEO of the World Land Trust.

John -   The exhibit we've constructed here shows at one end simulation of what the rainforest can look like - a lush, dense forest.  Then we have the ranger's hut, including a window, opening on to a plasma screen and actually a live webcam transmission from the forest.  So what people are seeing is what's actually going on in Brazil right at this moment.  And then the other side of the ranger's hut, we've got a little garden with a tree nursery showing how we grow the trees for reforestation projects, and also, the sort of tropical plants that people don't realise, without those tropical forest, we wouldn't have some of these plants - the sweet potatoes from Paraguay, the tomatoes from South America, the chilli peppers, the pineapples.  There are so many of our foods that we just accept because we get them in the supermarket.  But without the tropical forest, we wouldn't have them.

Meera -   What's the key message that you're trying to give to visitors this week?

John -   Well I think the key one here is that everyone thinks of the rainforest in terms of the Amazon  - and yes, 30% of the Amazon has been destroyed, but when you put that in the perspective of the Atlantic rainforest, the Mata Atlantica, where 93% is already gone it gives you an idea of what the real losses are. And some 40% of the species found in the Mata Atlantica are endemic to that region.  So we've got a real problem.

Meera -   What are the main ways you're going about addressing the problem?

John -   Well there's two ways.  One is buying up existing forests and putting that under strict protection and the other is buying land between protected areas, creating corridors where it may have been cleared in the past and doing reforestation projects on them.  You have a variety of ways of doing it - if it's only been cleared fairly recently, just by leaving it alone, it'll often regenerate.  Other areas cleared a long time ago will need more regeneration, we will need to do some planting.  For instance in our Brazilian project, they used 60 species of trees.  They concentrate initially on some of the fast growing ones because one of the big problems is getting them going. There's often African grass which is very invasive.  It is difficult for the trees to break through that.  So you need to create shade as quickly as possible. So we used the fast growing species, they provide the shade for the slow growing species, timber species, to grow eventually.

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Meera -   Now I'm just walking through the grand pavilion and there's a selection of plants that sort of really caught my eye, and that's the stand of the Hampshire Carnivorous Plants.  They vary greatly in their appearance.  Some of them are up to a metre in height.  They're tubes and some of them bend over almost with swan heads.  With me is David Tight who's manning the stand.  So what type of carnivorous plant are these?

David -   What we've actually got is a selection of carnivorous plants from around the world who have various methods of attracting flies usually by nectar, sometimes by pattern.  The plant produces a nectar on its lid.  The flies are attracted to that and the colouration of the plant, and what will happen is the nectar is a slightly narcotic, intoxicating juice which clogs up the fly's fleet at the same time while it's partying on the lid.  It'll get drunk, it'll fall in the tube eventually, once it gets round to the sweet spot and can't hang on, whereupon, it's constantly digested for the next three months over the course of the summer.

Meera -   So how does a plant go about digesting it once the fly has fallen in to the trap?

David -   What it needs is the vibration and the movement.  At which point, it releases an enzyme through the wall of the tube on the inside.  That's very similar to the enzyme within our stomach which breaks down the soft tissues in the fly, that the plant then reabsorbs through this walls of the inside of the tube.

Meera -   Therefore, getting its nutrition.

David -   Right.  Trace elements absorbed, plant has a sleep through the winter, wakes up again next spring and does it all again.

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Meera -   The theme of this year's show is biodiversity, due to it being the international year of biodiversity.  So what more fitting, than the Bradstone biodiversity garden!  So I'm now here with Paul Harvey Brooks who designed this garden.  So Paul, how in a space of 7 metres by 5 metres do you get the maximum biodiversity possible?

Paul -   Well the very definition of biodiversity is the number of species within a given space and here, we've tried to literally cram in as much as we can whilst making it very beautiful.  We've got lots of floriferous plants that are nectar rich.  They're very simple; the colours that insects really like and then we've finally have added into the way the garden's landscape features that are particularly of interest to certain birds and animals.

Meera -   We're currently sitting in a wonderful pillared porch towards the back of the garden and I can see a wide array of flowers in front of us.  So what particular flowers have you chosen and what array of insects have been attracted by them?

Paul -   In the flowering part of the garden, it was more of the colour and the structure which is important.  The colours that we're looking at are the kinds of colours that insects are particularly attracted to and that's from research carried out at Sheffield.  We see the colour as these rich mauves, lilacs and yellows, and obviously, insects are seeing them in UV light so it's different for them.  And then we looked at plants that kind of give shelter, give food, and things like the hedge where we've left the top slightly shaggy is particularly important for starlings and blackbirds because they won't nest in a perfectly flat hedge and directly fly into it.  They need to roost first and then fly in.  So if you don't have a tree, a hedge where you've got this kind of loose shaggy approach is much more beneficial. 

The other thing we've looked at are things like crevice nesting birds.  House sparrows in particular have declined by about 70% in 20 years and it's simply because we don't build in a vernacular fashion and we certainly don't keep older buildings as untidy as you could do to allow them to nest.  So we've made what we believe to be a very beautiful portico and you would find the crevice nesting bird there after a couple of years of it kind of settling in.

Meera -   And as well as birds, what else have you managed to attract?

Paul -   We've had damsel flies, we have blackbirds, blue tit, bees, honeybees.  It's just been a myriad but you know, a long term approach, this garden would also be attracting small mammals like hedgehogs.

Meera -   Now you also have a log wall here.  So what's that all about and how is that improving biodiversity?

Paul -   Well, in the urban garden, staghorn beetles are particularly prevalent or at least they were up until very recently when we became very tidy.  And so, what we wanted to do was create a kind of decomposing log wall, so the top layer is fresh logs and the bottom is really rotten and the staghorn beetles lay their eggs there. The larvae actually eat the wood.  So we wanted it to look good but also provide a really important habitat.

Meera -   So it's really doing its job?

Paul -   Well I think so.  People have been very complimentary and we've seen insects around.  In a way, a garden without all of this wildlife is fairly soulless.  For us, it's important to make it breath and the breath is the insect.

Helen -   That was Paul Harvey Brooks who designed the Bradstone Biodiversity Garden at this year's Chelsea Flower Show, and before him, John Burton, CEO of the World Land Trust, and David Tight from Hampshire Carnivorous Plants talking to Meera Senthilingam about how to help our environment from the rainforest right down to our own back gardens.

Dominic - This is interesting because we normally think that light travels in straight lines and so, when light comes into your eye, you know what direction it's come from, so you know what direction you're looking in.

But light doesn't always travel in straight lines. For example when it goes through a lens, we know it's bent and that's because the lens is made of a glass which has different refractive index from the air around it. Air also has its own refractive index which depends on the temperature of the air.

So, if you have hot air, it has different refractive index to if you have cold air. On a hot day, the sun will come down, it will heat the surface of the road and make the air close to the road very hot in comparison to the air above it.

That means that light rays are bent away from the road, and so, when you look down at the road, the rays are actually bending away from the road and back up into the sky, and you're seeing a patch of the sky in the road. Water also looks like that because water is reflecting the sky, making the sky appear in the road. So the mirage looks exactly like water...

Helen - Well it's all about the types of UV (ultraviolet) radiation that you've got - both in the sterilising bulb that you've got in your setup, and that's just all around us from the sun. [Sunlight] comes down through the atmosphere and contains UVA, UVB, and UVC. The most damaging form of UV is UVC, and that's what's in your sterilising bulb. It will be at a very high intensity and your water will probably get sucked through a filter and fed past this UV bulb, and that will do a very good job of killing off all those bugs that you don't want, using this very powerful form of UV light. But the UV light that's around us naturally from the sun, or even from a light bulb above your tank, that UVC will be very easily blocked by the water. Because it has such a short wavelength, it actually gets very easily disrupted and it won't actually make its way very far into the water. That's why nothing in the tank really gets affected by it. So you need that very concentrated intensive burst of damaging UV to keep the water clean, but otherwise, we do fine with the UV that bounces around in the room.

Chris - Because the stuff that we're normally seeing is a little bit of UVA, a bit of UVB, and we have an ozone layer which is really good at excluding most of the UV, including that UVC. So, in terms of sunlight, for the most part, we're protected.

Helen - Mostly protected. We still can get burned by A and B and different sun creams can help to block that, but in terms of the life that's in your tank, I think the water is enough to keep them safe from any bombarding UV light that's coming in from the surface.

Chris - Most filter systems have a little bioreactor in the bottom as well, where you have lots of bits of plastic and things with a high surface area. Good bugs, ones that you like, grow on there and then after the water's gone through the steriliser - which wipes everything out including the algal cells - it then goes through this bioreactor in the bottom of the filter which then re-seeds good bugs back into the water, as well as consuming some of the organic content which is how these filters actually work.

Helen - Absolutely.

Chris - I've seen some studies where they have looked at children, and also young juvenile rats who are being fed sweeteners or normal sugar. One suggestion that some people have made - I'm not sure whether the evidence for this is robust, but it sounds plausible - is if you feed juvenile rats on sweeteners, what happens is that the brain begins to misinterpret how many calories there really are in sweet things and it gets used to the fact that when you eat something which tastes that sweet and you don't get any calories for it, if you then do get into a situation where you can eat some sugary food, real sugar, sweet stuff, you then tend to over eat because the normal metabolic gate that would say, "I know how many calories I've taken in now because when I take in this level of sweetness, I normally get this number of calories." That's been thwarted by eating the sweeteners and as a result, it can lead to overeating and weight gain, and there's some evidence that people who are on these things for longer periods as children may then develop a habit or a sweeter tooth when they're older. But as I say, I think it's speculation. I'm not sure how plausible it really is. Interestingly, there's a paper that's come out this week. It's by Jay Slack who's over in America. They're actually looking at the bitter taste associated with sweeteners because you know when you eat something like saccharin, it has an aftertaste, and they found a chemical that they call GIV3727. The reason they call it that is because the real name of the molecule is 4-(2,2,3-trimethylcyclopentyl)butanoic acid. This blocks the receptor for bitter taste buds, so you could call it a bitter blocker, and as a result, things that were bitter tasting now taste sweet. So you can associate or accompany your sweetener with that molecule, and they've done it on humans, and people stop tasting the nasty bitter taste and they only taste the nice sweet taste. Isn't that nice?

Helen - It's a very nice idea in some ways, but first of all, you have to think about the scale of what you're trying to do here. The oceans are absolutely enormous. The numbers of fish we're catching are absolutely enormous, and I just don't think we have the technology, if we even wanted to go about this if we thought it was a good idea.

We are doing some smaller scale things. Some European eels for example are being "re-stocked" and I'm saying that in inverted commas because they aren't actually being bred in captivity, they're just being moved around the place because in some areas, they're doing very, very badly, so tiny baby eels are being moved to try and restock rivers, to allow people to carry on fishing. There are things like genetic issues you might need to consider as well. What sort of species? Where are they coming from to restock them? And I think we mustn't forget that the oceans have an incredible ability to restock themselves. We just have to give them a chance.

When we take away fishing pressure from certain areas, we do see an extraordinary recovery. So we really have to focus on oceans healing themselves. I think stepping in and doing it ourselves is not the approach. It's a case of letting the oceans do it themselves and giving them a chance.