Phosphorus: Essential to All Life But Are We Running Out?

Scientists have demostrated how to hide a secret message using everyday liquids, like cola, wine or coffee. Graihagh Jackson went undercover to meet Mark Lorch to find out more...

Mark - This group in Israel have come up with a way of encoding messages, and hiding messages, and then decoding them with common household liquids, so, it could be a glass of wine, or whatever. And so, that person that you've spotted over in that corner may well be that secret agent.

Graihagh - That's pretty awesome!

Mark - It is, isn't it. What they've done is they've taken a load of fluorescent molecules and combined them. Fluorescent molecules are basically molecules that absorb light of one wavelength and then emit it in another wavelength. Now the really cool thing about this molecule then is that the light it gives off is entirely dependent on the conditions it's in. If it's in coke, for example, it will give off a spectrum of light that's unique to the coke and, if you put it in a glass of wine, it will give off another spectrum of light, or a cup of coffee, another spectrum of light, and so on. So, using that, they've managed to come up with a way then of encrypting a message...

Graihagh - What I haven't told you Mark is that I'm actually as secret agent...

Mark - Oh are you!

Graihagh - ...And this interview - it's all a ruse so you can tell me how to decrypt secret message. So, say I want to send you message and we're going to make it really simple. I just want to say hello so Hi is the message we're going to send...

Mark - Just Hi. Okay that's... So the first thing we have to do is we have to turn the letter in 'Hi' into numbers.  So, let's say we make 'H' 1 and we make 'I' 2 - okay. Then what we have to do is encrypt that. What we do now is we take some of this molecule and we put it into a solution - okay. This, again, could be your coke, or your wine, or whatever and you then measure the spectrum of light given off by that molecule when it's in coke, for example. And then you assign part of the spectrum to each of the letters - the 'H' and the 'I'. Let's say 500 nanometers, we assign that to 'H' and 520 nanometers, we assign that to 'I', and then we measure the amount of light at 500 nanometers and 520 nanometers, and that gives us a number. So the amount of light given off, we measure that in arbitrary units. Let's say 500 nanometers that corresponds to 'H', we get a value of 5, and 520 nanometers which corresponds to 'I', we get a value of 10. Now what we do is we add the 5 and the 10 to the 1 and the 2. So 5 plus 1 equals 6 and 10 plus 2 is 12.

Graihagh - So what I'd write down to you is 6 and 12?

Mark - Yes. So you'd send that, however you like. In a letter, in an email in a tweet, whatever, you'd send me 6 and 12. Now, all I have to do is take that same molecule, put in the same solution that you've used - the coke again, let's assume, and measure the spectrum. And then, again, I'll measure 500 nanometers and 520 nanometers and get the values of 5 and 10 back out, take that off the 5 and the 12 to get 1 and a 2. We already know that the 1 corresponds to 'H' and the 2 corresponds to an 'I' and, from that, I get my message.

Graihagh - So what I want to know is would spies actually is this or is this just a bit of a gimmick?  Now that we've discussed it and everyone knows the secret...

Mark - Well, I did wonder about this because it was published in an open access journal, which makes you wonder...

Graihagh - No longer top secret...

Mark - No longer top secret but, just because you know how the system works, doesn't mean it isn't still secure. Nevertheless, I think it seems slightly strange.

Can you imagine a robot that's one hundred thousand times smaller than the width of a human hair? Devices this small called nanobots sound like something out of science fiction, but researchers at the University of Cambridge have this week moved us one step closer to them being a reality with the hope that one day, they'll be use them in the body for drug delivery. Professor Jeremy Baumberg spoke to Emma Sackville about this exciting development...

Jeremy - We've had this idea that you could make tiny machines - what people call nanobots that could actually go inside the body or they could do something useful for us and the problem has been we can't make them.

Emma - Why is it that we have problems making them?

Jeremy - When we try to make things move in water and they're very small, it's a bit like us trying to swim in treacle. It's very, very difficult so we need to actually swim in a different way. We can't do front crawl in treacle, we have to do something which is bit more like a bull terrier which flicks things backwards and forwards, and that's actually difficult to do and needs a lot of force, and we haven't found a way of actually making things that produce large force on this really small scale before.

Emma - But the research you've just done is actually looking at making something that moves on a really small scale and produce that kind of force.

Jeremy - Yes, we call them activating nano transducers, or ANTS for short, because they're strong things and they can move more than their body weight.  So what we've done is we've made some tiny particles which have got a coating on them and what these particles do, under the right circumstances, is they can actually produce a really large kick.

And the way it works is we take tiny little particles, in this case we make them of gold, and we've learned to coat them with a thin polymer, a bit like the polymers in our plastic bags, but this ones and gel and most of the time, at room temperature, it likes to have little fibrils of the polymer which spread spread out into water. But, if you just heated a tiny amount, a few degrees, what happens is it starts to hate water - it becomes hydrophobic, unlike many of us with swimming pools, and this gel will collapse.  So we have these metal nanoparticles and they want to stick together because they're trying to get away from the water, so they stick together really close. It's like a spring, they'll compress this polymer in between them. If they cool down very, very slightly, all of this reverses and now the polymer wants to spread out into the water but it's got to push apart the metal nanoparticles to be able to do that, so everything explodes. The nice thing is that we can do this heating and cooling with very weak beams of light and so we can actually make a little engine which is powered by a very small beam of light.

Emma - Great. Well, can I go and see some of them in action?

As Jeremy took me over the lab, I tried to mentally recap exactly how these ANTS worked. So we have tiny bits of gold, coated with a gel and below 30 degrees they like water and they really spread out. If we heat them up or shine a light on them, then they stop liking water and they all scrunch together just like a spring, as Jeremy said. PhD researcher Sean Cormier joined my in the lab to show me this change in action.

Sean - Some of the ANTS - a nice red colour and you just have to heat it up above 32 degrees.

Emma - Okay, so we've got like a little tiny capsule with a red liquid in and it's just in an oil bath at the moment so we're just heating it up, and what exactly are we looking for?

Sean - So what will happen is all the particles will actually change the way they interact with the water, and they'll change colour because they'll stop liking the water, and they'll collapse on top of each other, and now they're very purple.

Emma - Yes, okay.  So the liquids actually changed from red to purple.  It changed pretty quick! How fast have you been able to measure it changing?

Jeremy - In fact, it's too fast for us to measure at the moment and that's why it gives such a big force and, in fact, it's gone back to red. So what happens is all the ANTS cluster together - it goes purple, and as soon as it cools they explode. So that's how we keep track of it by looking at the colour.

Emma - It feels very weird to be in a lab without wearing lab specs, I must say!

Jeremy - It's very safe at the moment but you're right.

Emma - Despite the name, the gel Sean and Jeremy showed me really looked nothing like an ant. I asked Jeremy whether he had any specific ideas about how they could use the ANTS or whether there are any future applications.

Jeremy - So there's this area of science called microfluidics where you try and make little chemical refineries in some ways but shrunk down to the size of a chip, so that's the idea for one of the earliest applications. For applications where we put them in our body yes, indeed, we really don't know how to do that yet. One of the good things is we don't just have to use light to make these things open and close so it's actually a rather generic technology. Yes, we have to find out what's the killer application or maybe the non-killer application for the body!

Emma - And if we did want to use them for these kinds of applications, how easy is it to make them?  Is the large scale synthesis of them feasible?

Jeremy - Yes, that's the amazing thing.  All the components, as it turns out are completely commodity; we can buy them on a very large scale. So, in fact, already there's nothing stopping us scaling these up and making a kilogramme of these ANTS. We can replace the gold nanoparticles that we use at the moment with silver nanoparticles, which is cheaper, and we can use nickel or copper as well, that should be fine so making them is not the problem. The question is how to turn them into something useful and that's going to take us the next year.  We want to make some of these demonstrators in the next but, of course, what we really want is  a lot of other scientists to join us in this quest.

If you've followed environmental stories over the years, you'll know this tune. Scientists and environmentalist have long been singing off the same songbook when it comes looking after our planet - we take too much oil and gas out of the ground, we cut down too many trees and inject too much carbon dioxide into the atmosphere...

But drum not often banged is the dwindling supply of phosphorus. It's is an essential element for all life. It makes up our DNA and all organisms need it for energy. It cannot be replaced; there is no synthetic substitute: In other words, without phosphorus, there is no life. And so this week on the Naked Scientists, we investigate whether we're running out of phosphorus for fertliser. But first, Graihagh Jackson went on a field trip to the outskirts of Cambridge to find out how us Brits were once self-sufficient in phosphate production thanks to dinosaur dung! -  And to ask Dr Robert Evans whether we could be once again...

Graihagh - Hi Bob.

Bob - I hope you haven't been here too long?

Graihagh - I have but I've been enjoying the sunshine. I didn't realise how long it would take to cycle.

Bob - Well, I've got a tremendous cold...

That's Dr Robert Evans from Anglia Ruskin's University and, despite his tremendous cold, he still let me pick his brains about phosphorus.

Robert - Oh phosphorus. P, phosphite. It's an element that most plants need to grow. It's part of proteins, it's part of your body, it's part of plants. Most soils in Europe, and I think probably worldwide, are short of phosphite so it's a key ingredient for plant growth. So if you want to improve yields, you've got to put these kind of things on.

Graihagh - I've read all sorts of weird sources of phosphate. Things like blood and bones and all sorts of things.

Robert - Yes, that's right. When phosphate fertilizers were first devised, it was mainly using rock phosphate and then when we had the phosphate nodules here, the dinosaur poo, it was obviously much cheaper doing it here.

Graihagh - What was this dinosaur poo? How was it formed?

Robert - Cambridge Greensand was forming over about 100 million years ago and, whether it's really dinosaur poo or whether it just looks like dinosaur poo, I think there's quite a bit of argument about that.

Now then, we are literally about there. That's Coton, the village there.

Graihagh - These instead of ordnance survey's they're like geology surveys?

Robert - The geology maps and these, in places, are almost identical but the geology maps we're looking at the rock depth. We were looking at it in the top 1.2 - 1.5 metres. So, if you look on here, Cambridge Greensand is literally in Cambridge - that's it. 92a.

Graihagh - This is sort of a light blue colour we're looking at and you're right, it is a very thin stretch that goes from sort of Southwest Cambridge all way through North/Northeast Cambridge. But, what I notice is, all of Cambridge urban area is also in this light blue colour.

Robert - That's because it's urban.  Nine on this map means disturbed ground so it's a very similar colour to urban.

Graihagh - So it's not that Cambridge is sitting on a huge supply of....

Robert - It is actually. There's probably quite a lot of it. In places it was really widely excavated and there's quite a lot of - I think the outskirts of Cambridge was excavated for the coprolite diggings.

Graihagh - And on the outskirts of Cambridge is Coton where one of the many excavations of coprolite took place. We wandered over to an adjacent field to a rather underwhelming plaque...

This is a tiny sign...

Robert - You have to get down on your hands and knees to read it. It's not very spectacular but I was absolutely gobsmacked when I saw it.

Graihagh - Gobsmacked because this sign represents a significant part of history - The East Anglian Goldrush.

So coprolite is the commercial name for phosphatic nodules which were formed in the rock under your feet, deposited around 110 million years ago. When experiments showed locally mined coprolite could be turned into fertilizer much more cheaply than imported bone meal, the great coprolite rush of the 1850s was on. And there's a picture as well actually of the diggings near Orwell and Barrington.

Robert - The industry grew and landowners, and tenants, and agricultural workers alike could make money from the new industry. It's just amazing how quickly the labour market expanded.

Graihagh - Something like Barrington, it said before the coprolite industry there was no-one living there. During the industry there was 155 and then afterwards there were 3. So, actually, Barrington was born because of coprolite?

Robert - Yes. It says in the peak, 1877, Cambridgeshire produced almost all of the 54,000 tons of raw phosphate used for manufacture in Britain. So, in actual fact, we were self-sufficient in fertilizer. That was absolutely gobsmacking!

Graihagh - Given today that we're not self-sufficient at all.

Robert - In practically anything! The industry waned in the 1880s as cheaper phosphate was imported from North America and today, most of the coprolite diggings like this one are filled in and the land returned to agricultural use.

Graihagh - Does that mean we can be self-sufficient again?

Robert - No - it's all been dug out.

Graihagh - All of it?

Robert - Well it's something like 40 out of thousands of acres that's left. So there's probably no more coprolite diggings to be done.

Phosphorus is needed for crops to grow, so could we breed plants that don't need it? Or use bactieria to unlock more from the soil? Dr John Hammond talked through the possibilities with Graihagh Jackson...

Graihagh - Surely the first plan of action should be to reduce the amount of phosphorus we use in the first place - right?

John - Yes, that's right. Phosphorus is essential for growing our food so can't do away with it completely. We have to have some inputs into the system and, as we've already heard to the second world war, the amount of phosphorus we were using has increased probably more than it should have done but we are on the case now and looking at that. And certainly in the UK over the last 20 or 30 years, the amount of phosphorus going into our fields has roughly halved.

Graihagh - But that's not enough then? I mean what else should we be doing or can we be doing?

John - Well, there are a number of things that we can look at. There are land management issues looking at creating a healthy soil so the phosphorus in there is turned over.  Looking at alternative fertilizers and sources of phosphorus from things like sewage or we can look at breeding crops which are better at capturing the phosphorus in the soil and using it more efficiently.

Graihagh - Because I suppose there are places in the world like Australia, I'm thinking, where it's really poor in phosphorus. So there are plants that grow there so can we just steal some of their tricks of the trade and use them in our crops in the UK.

John - Yes, that's one of the types of things we're looking at doing. So, these plants in Australia live on very little phosphorus and yet they're able to produce large amounts of biomass. They have a number of attributes in their root systems and in their leaves that allow them to capture phosphorus more efficiently by exuding acids and enzymes into the soil to extract the phosphorus. Making very good, close relationships with thing like bacteria and fungi in the soil to help them capture the phosphorus and very extensive root systems that can mine the phosphorus from the soil.

Graihagh - And these bits of research you were mentioning there. Have they been successful? Have we been able to breed them into other crop varieties?

John - There's been a number of attempts to do these things. There's a couple of examples. For example, in China, there's some soya beans that are now available commercially where they've over-expressed in the roots some of these enzymes which are released from the root into the soil, and these enzymes can break down some of the phosphorus locked away in organic compounds. They are more efficient at capturing that phosphorus and producing higher yields for less phosphorus input.

And another example is in beans, where we've got this phenotype or characteristic of the root system where they are able to put a lot of their roots in the topsoil. Because phosphorus is very reactive, it doesn't move very far in the soil, it tends to stay in the top 30cms. So, if you can get a plant to put a lot of it's roots into that area of the soil, it can capture more phosphorus.

Graihagh - Is that not a bit of a risky thing to do though? I'm thinking if there's a drought or anything you want deep roots so, I mean, you can't really put all your eggs in one basket, surely?

John - No, no, that's it.  So that is one of the downsides to that approach is if you put all your roots in the topsoil, you're at risk of maybe not being able to capture maybe water and nitrogen which are further down in the soil profile. So there has to be some aspect of plasticity in the root system that allows the plant so respond to an appropriate stress,.

Graihagh - And you mentioned this sort of inaccessible phosphorus in the soil before and how these root system produce enzymes to get this phosphorus out. I wondered if you could just sort of unpick that a little bit for me?

John - Well, a plant can only take up phosphate which is in the soil solution and the rest of the phosphorus in the soil is either bound to the soil particles through very strong bonds or in organic compounds, so dead plant material or dead microbes. But, in the soil, there are fungi and bacteria which have to scavenge that phosphorus as well from those sources, and they have these enzymes and ability to release acids into the soil to release that phosphorus from it. So plants, historically, are very good at making mycorrhizal symbioses, which help the mycorrhizal fungi catch the phosphorus for the plant and, in exchange, the plant gives the fungi some carbon so the plant can encourage those microbes to grow and help scavenge the phosphorus for them.

Graihagh - I imagine though trying to unpick what microbes are doing that job is next to impossible. There are thousands, if not millions of species of microbes in soil so, how do you go about finding the right one?

John - It is very tricky and up until probably the last five or ten years, it's been nye on impossible because a lot of the microbes in the soil won't grow very well in the lab. So it's very difficult to take them out of the soil and find out what's there.

With the advent of new sequencing technology, we've been able to take the DNA out of the soil and sequence that DNA, and start looking and identifying all the microbes that are there. We are actually part of a new BBSRC funded project where we're looking at, not extracting the DNA, but actually extracting the protein and sequencing the proteins that are in the soil around the roots, so that we can identify the types of enzymes that are active in the phosphorus cycling process, but also the microbes that those enzymes came from in the first place.

Graihagh - So you can sort of match them together and then, hopefully, design some microbial soil magic dust that you can sprinkle on and get your plants to extract phosphorous magically?

John - That's the idea.

Graihagh - I just have a bone to pick with you because, surely, you're kicking the can further down the road for future generations to pick up though because we're still reliant on this phosphorus despite reducing it?

John - Certainly. There's no way we can produce food without that so it's still a question of minimizing the amount we actually use, and using it as efficiently as possible in the farming system. But we do need to look at a whole host of mechanisms to close that phosphorus loop so we're not losing it to the water where it's causing eutrophication, and bring it back onto the farm so we're not washing it all away.

In 2050, we'll hit 'peak phosphorus' just when our population is at its highest and demand for food will be high. What can you do as an individual to reduce your phosphorus footprint? Kat Arney put this to Dr John Hammond and Dr James Dyke...

Kat - It's not all doom and gloom then, there are things we can do to close the loop and lessen the load of the loss of phosphorus but is it going to be enough? James Dyke and John Hammond are still with us. John what do you think because I guess we're facing a growing global population, we've got issues of climate change and now, as has become clear, problems of water shortage potentially, and a phosphorus shortage. This sounds like a doomsday scenario?

John - Yes, I think there is sort of a perfect storm scenario that we could envisage coming up in the future where we've got all these competing interests coming together - population, food supply, climate change. But there are things that we can do, and we are doing, to try and mitigate that but there's no single silver bullet. It's a whole host of things, I think, we need to do.

Kat - So what can we do? Say me as an individual, I can do things to reduce my carbon footprint, I can cycle, I can try not to take so many flights - what can I do for phosphorus footprint?

John - Well, there's a couple of things. Firstly is reducing our meat consumption. Producing meat uses far more phosphorus than it does producing vegetables and grains. Going for a more vegetarian based diet would certain reduce it and research suggests, if we all went vegetarian, we'd probably reduce the amount of phosphorus we're using in our food production systems by 25 to 45%.

Kat - And James - what about reducing things like food waste? Are there other things we can do as a whole society?

James - Indeed, yes. So, in a developed nation context we do throw away tremendous amounts of food so that is throwing away a tremendous amount of phosphorus. In developing nations, the main problem they've got is getting the food from the field to the market before it rots. One kind of optimistic slant on this is, given how prodigiously wasteful the food production system is on earth, there's an awful lot of fat to cut, so there's an awful lot of savings we can make.

Kat - It just seems all round if we can do things to reduce our consumption of water, of fossil fuels to release less carbon, and use less phosphorus. This is generally all round a good thing so generally reducing consumption is what humans should be aiming to do on a personal and society level?

James - Yes, but if you look around that's not the kind of message that you tend to get on a day to day basis. We are continually compelled to consume more. So, by the middle of this century when there'll be the greatest number of mouths to feed - there'll be 9 billion people - we're going to have to produce 50% more food, gain access to 50% more water, generate 50% more energy, all at the same time as reducing our impacts on the earth's climate. And that may, unfortunately, be around the same time we could see a peak in our supply of phosphorus so, whilst there are lots of things we know we have to do, there's lots of things we can do individually, society, commercial and governmental contexts. This really is a very significant challenge that I think it's fair to say we're not really addressing right now.

Kat - But, presumably, every little will help.

James - Absolutely - do your part!

Kat - I think I shall try and have more meat free days - that's what I'm going to commit to.