Good morning everyone and welcome.
Today we have three talks and then we have a round-table discussion.
The first speaker is Richard Roberts from New England Biolabs.
But the discovery he made in 1977 about the mosaic structure of genes was made
when he was working in Cold Spring Harbor Laboratories in Long Island, New York.
He received the Nobel Prize 1993 for the discovery of split genes.
And the title of his talk is why I love microbes, Dr. Roberts, please.
(Applause).
Thank you.
Well, what I’m going to try and do today is to give you some idea of why I find microbes absolutely fascinating.
I think they have so much going for them that I would encourage all of you
to perhaps think about working in this area at some point.
One of the things I like about microbes is that they’re essentially very simple organisms.
And it seems to me possible that if we had enough effort put into studying them,
before I die we might actually understand how the very simplest microbe works.
And I think all of us as biologists would like to understand how life works.
We’re not going to understand how humans work in my lifetime, perhaps not in your lifetimes either.
But I think we may be able to understand how a microbe works.
And for me that would be a very exciting possibility.
The microbes also have the great advantage, from my point of view, that most of them are undiscovered.
Less than 1%, perhaps less than .1% of all the microbes on this planet have actually been discovered,
characterised in the laboratory or grown in the laboratory.
Most of them we can’t grow.
Part of this is because many of them will only grow when there are two or three or four, all growing together.
They need one another in order to be successful in life.
Many of them also live in incredibly inhospitable places.
And I will show you one or two of these microbes.
They also have one very remarkable property.
And that is that they live with us, our bodies are literally crawling with bugs of one sort and another,
we have them on our skin, we have them in our mouths, we have them inside us.
Everywhere you can imagine microbes live.
And I will show you a little about this, too.
So we’ll start off by taking a quick trip through the environment.
I’ll show you one or two bugs that I find particularly interesting,
and then we’ll head into the human body and human health and the kind of organisms that live with us.
So if we go on to the next slide, I want to use this just to show you how microbes –
and by microbes I’m talking about bacteria and archaea, and these are the three kingdoms of life, shown here.
The archaea originally were thought to be bacteria, in fact they’re a completely separate kingdom of life,
as shown by Carl Woese in 1977.
And what this tree of life does is to try to show you how everything is related to one another in terms of its diversity.
So for instance the eucarya, the large organisms that you see, plants, people, giraffes, rhinoceros,
anything big, mice and so on, all of these form up here.
Many of these down here, giardia and so on, are very tiny microorganisms, microscopic.
And all of these other organisms, the bacteria and archaea, you can see they’re a long way away, very distantly related to us.
And we sit up here, this is homo and this is maize,
so we’re much more closely related to maize than many things that you might have thought of,
we’re a long way away from the bacteria.
But notice here the mitochondria, the red organisms, these are small organelles that live inside ourselves,
that produce energy for us and these are very closely related to the bacteria.
I’m showing that the human cells, the human genome has actually something
that has acreated from many other different genomes over time.
So most of the diversity on this earth are microbes, in fact most of the mass is on microbes.
This may be hard to believe, you sort of are used to looking around and you see all this vegetable matter
and lots of animal life and so on.
You can easily be confused into thinking that this is most of the mass of life on this planet.
It’s not, the microbes are most of the mass of life on this planet.
Not just with us but in the seas, the seas are absolutely seething with microorganisms.
Even if you dig three miles down into the earth you will find microorganisms,
typically about 10 to the 5 to 10 to the 6 cells per gram of material, three miles down in the earth.
So these things are everywhere, they’re in the Antarctic, under the ice, everywhere you can imagine.
And one of the reasons that you don’t really appreciate how much there is, is because you can’t see them,
these are microscopic organisms, you have to look under a microscope to find them.
Now, the first slide that I’m showing here is a photosynthetic organism.
And in fact this organism is rather interesting in the sense that it was the original polluter of this planet.
When life first began on this planet, it began in an anaerobic environment, there was no oxygen around,
most of the oxygen was wrapped up in minerals inside the rocks of this planet or in water.
These organisms started doing photosynthesis, they started producing oxygen,
and in fact they wiped out most of the existing life that was all anaerobic, that didn’t like all of this oxygen around.
And you can see they’re very nice organisms, they form these beautiful long chains
and every so often you see one of these slightly larger heterosis, very strange little form of the microorganism.
And these can live anaerobically whereas the others live aerobically.
If you look in soil, anywhere where there is material rotting, you will find things called myxobacteria.
They look like little mushrooms, except you can only see them under the microscope.
And they form these beautiful little fruiting bodies, they’re very nice little fruiting bodies.
They’re essentially bacteria that are able to differentiate.
They can produce different kinds, different forms of cells and different forms of acreations of cells in order to survive.
These things are just all over the soil.
Many of them are this beautiful orange colour, they’re very, very pretty.
Sometimes you see them as films on rotting wood.
But there are many, many of these things, without them we would actually probably be full of debris
of one sort and another, they’re very important in terms of getting rid of waste material.
Now, this organism I love, it’s an example of a spirillic bacteria, this one is called aquaspirillum magnetotacticum.
And this is a guy that lives in the oceans and has within it a very interesting structure, shown here in black,
that is an acreation of ion and it’s a magnet.
So this organism has formed a magnet within itself and it uses this to navigate.
And it swims in the direction of the earth’s field.
If it’s in the northern hemisphere it likes to swim north, if it’s in the southern hemisphere it likes to swim south.
And it’s also very sensitive to the force fields and so it actually swims underwater and swims away from the surface.
We don’t really know why it does this, it’s just a behaviour that one can observe, there are several theories,
some people think that it’s swimming to get away from predators, others think it’s swimming to get to food.
But why it would use a magnet to do this is completely unknown.
And there’s actually a whole bunch of organisms, some 40 or 50 different species of organisms are now known
that can do this same sort of thing, they have little magnets in them for devising, for getting around.
This is something else in the ocean, beautiful tube worm.
These things live on these deep sea vents, you know underneath the oceans there are many volcanoes,
many hot vents in which we have magma and other materials spewing out of the earth
and sometimes these are called ‘deep smokers’, ‘dark smokers’.
They were discovered about the mid 1970’s by deep diving oceanographic vessels, mainly from Woods Hole.
And these things have magma, they have steam coming out at incredibly high temperatures, anything up to 1,000° centigrade.
And this is right in the middle of the deep ocean very often and so you have these great thermal changes
that take place from the deep vents with material at 1,000° out into the ocean
which is typically about four or five° centigrade and so you get a big thermocline develops.
And it turns out that there are many organisms that like to live in this zone between the actual vent and the ocean
and where temperatures vary from anywhere from 100°, suddenly coming down to 5°,
and there are not only many bacteria and archaea that live there,
typically the archaea love to live in these kinds of environments, but there are also eukaryotes.
And one of the eukaryotes is this tube worm.
So this is actually a worm, this is the sheath of the worm and this is the plume.
And the centre of this worm is actually a massive bacteria.
In fact without the bacteria the worm couldn’t exist.
So the bacteria are busy taking advantage of all of the minerals
and all of the energy that is coming out of this deep vent and using it to manufacture materials that then keep the worm going.
So very bizarre, and you find these everywhere.
So let us say, you know, you might have imagined one of these things could have arisen in one particular vent,
they then spread everywhere.
Wherever these things occur in the oceans, you find these tube worms and you find these beautiful bacteria that live within them.
Now, when we go to Yellowstone National Park - and there are many parks like this
but I’ve not been to one that’s quite as nice as Yellowstone - this is where I do my little tourist bit,
I think if ever you get the chance to go to Yellowstone National Park, you should.
It’s just an amazing place, it’s a volcanic caldera where there are many hot springs, many geysers,
the ground in general is extremely hot in many parts of Yellowstone still.
And there are wonderful examples of bacteria and archaea that live there.
And when you look around some of these thermal pools, so here’s a thermal pool
and here’s some hot water that’s running down into it, you see lots of these phototrophic organisms that are living here.
They show up with these beautiful colours, they form bacterial films.
If you look down through these films you discover that at the very top
there are organisms that are using one wavelength of light in order to do photosynthesis and get energy.
And as you go down you have bacteria that are using whatever light is left.
And so by the time you get down really only a few centimetres and there is no light then penetrating,
because it’s all been used up by the bacteria that have developed to take advantage of it.
And they form just these beautiful colours all the way around these pools and they’re all films of bacteria.
This is where for instance the enzyme Taq polymerase from thermos aquaticus came from.
A man called Brock, a very famous microbiologist first found this organism at Yellowstone,
and this is in fact the place where we’re now able to do PCR and all these other wonderful things,
because of the organism that came out of this hot spring.
Typically organisms here live anywhere between 80° and 100° centigrade, imagine at 100°C,
normally your DNA is completely denatured.
But these organisms have found ways to keep the DNA strands apart.
Now, another nice thing you see in Yellowstone are these beautiful sulphur springs.
This yellow colour here is all elemental sulphur and it’s caused from this archael organism, sulfolobus and sulfotaracus,
which is able to take advantage of the hydrogen sulphide that is coming out of this spring.
And they can then oxidise that, produce sulphur and in the process gain enough energy to live.
Wonderful organisms, many, many examples of this when we look around.
Now, I want to move away from the environment at large and talk about our local environment.
Talk about humans and the bacteria that live with us.
We often are not completely aware of all the bacteria that live with us until we get sick.
Many of us, you know, we come down, we have a nasty infection that’s caused by a staphylococcus perhaps.
When I was a child, before there were antibiotics, every time I would get a cut on my leg
it would always get infected and turn yellow and nasty, absolutely awful.
And now of course you can treat all of that with antibiotics, although we probably use antibiotics more than we should.
But there are many, many things that come along and cause us problems and I will take you through
and talk to you about one or two of these organisms that cause problems.
Because even when they cause problems, they’re still extremely interesting organisms, they have wonderful lifestyles,
they’re able to do all sorts of interesting things.
And there are also many organisms that live with us that are completely harmless.
And in fact others that are very, very good for us, things that we call probiotics and I will finish by talking about those.
But I wanted first just to talk a little bit about the cells that we have, and to compare humans with the bacteria.
So in a typical human there are about 10 to the 13 cells, that is human cells, and there are about 10 to the 14 bacteria.
So there are 10 times as many bacterial cells in a typical human as there are human cells.
The number of different strains in humans is 1, in bacteria I’d put this down as greater than 400.
In fact the bottom line is we really don’t know in any great detail
just how many different kinds of bacteria there are living with us.
And there are several projects underway at the moment to actually look at all of the bacterial genomes
that are associated with humans.
People are going around taking samples of skin, taking samples from the mouth, from the stomach and so on
to try to get a feel for just how many strains there are.
And I think this could easily be actually 10 times as many as this, there could easily be 4,000,
and we really wouldn’t know at the present time.
Most of these organisms we can’t grow, the only reason we know they’re there is because we can study their DNA,
we can look at their ribosomal content, the ribosomal DNA content and get some idea of just what the diversity is.
But it really is quite immense, these things are everywhere.
If you look at the number of DNA basis - in a typical human cell there are about three billion –
if you tot up all of the DNA basis, the individual genes, the individual sequences in these various strains of bacteria,
we’re talking about maybe a third as many DNA basis, but that equates to many more genes.
So these three types 10 to the 9 DNA basis in a human cell, the estimate is 30,000 genes, maybe that’s down to 25,000,
it seems to be going down all the time, the number of human genes we have.
And the bacterial genes are probably going up and up and up.
And so there are many more bacterial genes that are associated with our bodies than there are human genes.
That's something also to think about.
The bacterial population is very, very much greater than ours in terms of its diversity.
Just to give you some idea of where you typically find large numbers of organisms.
On skin you have staphylococci, there’s a lovely organism called staphylococcus epidermidis,
I sometimes show a slide of this thing, this organism lives inside the pores inside your skin
and it’s essentially impervious to anything we do.
You can wash your hands and your arms all day and these organisms don’t mind at all
because the soap really just never gets to them.
They’ve found some very good ways to hide.
There are corynebacterium, lots of different species here, I don’t propose to go through them all.
In our mouths we have a very interesting set of organisms.
About 1 in 10 of all of the organisms that we can recognise as living in our mouths
have we ever been able to grow or even just to identify in any reasonable way.
Most of the organisms we don’t know what they do, we don’t know why they’re there, and we have very little knowledge of them.
In the respiratory tract all sorts of organisms, too, the gastrointestinal tract and the urogenital tract.
And of course, here you have lots of organisms that can cause problems.
And many of these organisms are pathogens, but many of them are not.
And in fact, even the ones that are pathogenic in some ways are a little beneficial,
because some of the organisms that we have, that are actually good for us,
are producing compounds that keep these pathogenic organisms at bay.
There’s a constant fight between microorganisms and they all want to live in this little niche.
And so many of the organisms that are actually rather good for us are producing compounds
to keep these pathogens at bay, which is a good thing.
Now, I love to show this slide, it shows exactly what happens when you sneeze without stifling it.
And this is the way that an awful lot of these pathogenic organisms like to get around.
They like to live in the nasal passages, in the throat and in the mouth and so on.
And so this is the kind of aerosol that is produced every time that you sneeze.
And of course these have microorganisms in and they’re spreading around all the time.
Of course tuberculosis, you probably heard about the recent scare in the US, tuberculosis gets around this way
and is in fact an incredibly dangerous organism in terms of its ability
to pass from one human to another, very, very infectious nasty agent.
Now, the history of disease kind of goes back to 1877 and in fact it was anthrax
that was the very first organism that was shown definitively to be the producer of a disease.
This was shown by the great microbiologist Robert Koch.
He then went on and found a whole bunch of other things,
came up with the rules that determine whether or not we could declare that something was the causative agent.
And coming down here, you’ll see all sorts of really nasty diseases and that are caused by these microorganisms.
One or two of these I will tell you something more about.
But there’s been a long history of this and it’s obviously been something that microbiologists have been very keen to look at,
and one would always like to know what are the organisms that are causing disease.
And of course then how to deal with them, how can we stop them.
Now, one organism that I like to talk about quite a lot is helicobacter pylori,
this is an organism that lives in your stomach, lives at extremely low pH,
it lives in the lining of the stomach, in the endothelium.
Two years ago this organism was the subject of the Nobel prize in medicine
when it was awarded to Marshall and Warren who were the first people to show that this organism was in fact the cause of ulcers.
Prior to that the pharmaceutical companies thought that all you needed to do if you had an ulcer was to take an antacid,
this would solve the problem of the acid that was present in the stomach
but it did absolutely no good at all for the cause of the disease.
And Barry Marshall did the classic experiment that many doctors like to do,
he was convinced that this was the source of the infection,
it was the cause of ulcers and so he grew some in the lab and drank it.
And sure enough, within a few days, he came down with an ulcer
and fortunately the helicobacter that he drank was susceptible to antibiotics and he was able to cure himself very rapidly.
And in fact you can cure most causes of ulcers through helicobacter pylori just by taking antibiotics,
of course the pharmaceutical industry didn’t like that very much because the sales of antacids went way down.
But nevertheless this is the cause.
And this is an actual helicobacter pylori here,
this is the bacterial cell adhering to one of these epithelial cells lining the stomach.
And you can see it causes a very close interaction.
And in fact it is known that helicobacter pylori can cause cancer, it causes stomach cancer
and it can also cause oesophageal cancer if you have acid reflux disease,
we don’t know how this happens but the evidence is very strong that it can do that.
Now, most of us who live in the western world no longer have a lot of helicobacter pylori in our stomachs.
If you live in the developing world almost everybody is infected, you pick it up at a very early age.
But in the western world we take so many antibiotics that we’ve usually killed off this population.
And a man called Martin Blaser at New York medical school has recently been looking at this organism
and finds a very strong correlation between whether you have a helicobacter pylori infection
and whether you’re susceptible to asthma.
And it turns out that if you have a very high concentration of helicobacter pylori, a good infection going,
you almost never get asthma.
And as the amounts of helicobacter go down in the population, up goes the rates of asthma.
He believes there’s a causal connection here, it’s still too early to know for sure,
but it does point out the fact that there are many bacteria who live within us,
that we indiscriminately get rid of by the poor use of antibiotics,
and when we do that there may well be all sorts of unintended consequences.
I show this one, this is a very nice organism, just a beautiful slide, it’s one of these spirillum organisms,
it’s called borrelia, it’s the cause of lyme disease.
Vibrio cholerae causes the disease we know as cholera.
However, vibrio cholerae is really interesting,
it’s a small microorganism that lives in conjunction with a large eukaryotic organism called volvox.
And it actually sits on the surface of the volvox to a point where if you have a cholera infection going,
and you believe the water is contaminated, merely by filtering the water through something like a very fine thread,
something like a sari, you can actually get rid of most of the vibrio organisms in the water.
Very simple public health measure can be useful here.
This is another spirillum and this time treponema that causes periodontal disease.
Yersinia pestis is the cause of plague, this was the organism that caused the Black Death in Europe,
that decimated the population of Europe in the Middle Ages.
I always like to show the next slide, this is one of the little bubos that is produced by this organism.
And when you get a really good infection going, then you get a very severe gangrene in the fingers, in the toes and thorax.
By the time you reach this stage, there’s almost nothing can be done about it.
But if you catch it early it’s very susceptible to antibiotic treatment.
And I want to close just by talking a little about lactobacillus sake,
lactobacillus is one of these organisms that we think of as a probiotic.
They’re very good for you and this organism you get in yoghurt, wonderful thing to eat lots and lots of yoghurt if you like it.
I personally don’t like it but I would recommend it to all of you.
These organisms produce compounds that will keep many of the pathogenic organisms at bay.
There are many other such organisms that do this, bifidobacterium is another one that you sometimes find in yoghurt,
but there are really lots and lots of wonderful microorganisms that do in fact do wonders for you,
you want them in your bodies, you want them around because they’re keeping the pathogens at bay.
And I want to close just by asking you to think about something I find quite remarkable.
So here we are, we’re humans, we’re walking around, we’re absolutely full of bacteria, they’re living all over the place,
they make a very nice living with us.
When we evolve, as humans evolve, so the bacterial populations evolve, too.
The two are really in a tremendous symbiosis, we’re both evolving together.
And it’s rather easy to think that perhaps humans were invented by bacteria in order to provide a nice place to live.
Thank you very much.
(Applause).
Thank you very much, you did very well on time, so we have time for questions.
Are there any questions here?
QUESTION. I think nowadays lots of people use antibiotics and I think it’s maybe a damage to our human flora of microorganism.
Do you think it’s quite a severe problem we use too many antibiotics?
RICHARD ROBERTS. Yes, so antibiotics, you know, they really are the wonder drug,
they were the wonder drug when they came along and we very much abuse them.
We feed them to cattle and so they get into meat, they get into our food supply.
Certainly in the western world the slightest hint of an infection, whether it’s a viral infection,
for which antibiotics will do no good at all, or whether it’s a bacterial infection where they will work,
we use way, way too many.
And that is really clear, if you look at tuberculosis as one of the best examples of this.
When I was a kid, tuberculosis was a major problem, if you had tuberculosis, in England you were put into a sanatorium,
you were separated from the rest of the population to stop it spread.
Along came antibiotics, we could cure microbacterium tuberculosis and so everybody stopped worrying about it,
now we’ve reached a point where the microbacterium
- it’s a very slow-growing organism and you need to do a very long treatment to cure it –
many, many strains of microbacterium are drug resistant and god forbid you should ever go to prison in Russia,
but if you do, the odds are you’ll come out of prison with a nasty tuberculosis infection.
Tuberculosis kills more than a million people a year around the world
and the US government in its wisdom stopped funding research on microbacterium many, many years ago.
They’ve only just started putting more money into it and we have a major problem again with tuberculosis.
And so, yes, we’ve done a terrible job of actually handling the antibiotics that we had.
And there are very few new ones, sort of new forms of antibiotics in the pipelines.
There are a few beginning to appear now, but we’ve gone through a long period of neglect.
QUESTION. I’m a medical doctor from Pakistan, I was fascinated when I found that intravesical tuberculosis therapy
was being used for bladder cancer.
And when I looked at the literature, I found that many viruses are being used as anti-tumour agents,
do you think that this is a promising area of microbes being used to treat cancers?
RICHARD ROBERTS. Yeah, so the question here relates to the use of microbes and viruses in order to treat cancer,
and I’m afraid I don’t know anything about that.
I’m completely ignorant on that front.
I know about bacteria phages being used to treat bacterial infections.
This is something that was taking place in Russia for a long, long time.
But I know nothing about using microorganisms to treat cancer.
So maybe we can talk about that afterwards, because I would love to hear some more about that.
QUESTION. I just wanted to know, a lot of companies are selling now changed food with probiotics,
is there really any evidence that it is much better for us to buy this more expensive food.
RICHARD ROBERTS. Well, I think it’s really hard to know.
The problem with health supplements, health food supplements is they’re not well regulated
and so it’s an obvious market for any charlatan to come along and try to sell you snake oil.
I think for some of the probiotics, when they tell you exactly what is in there, and especially if they have lactobacillus
or if they have bifidobacterium in there, there’s a good chance that they will be useful.
But I think equally there are many things on the market that one would do best to avoid.
I think if you really want to go the probiotic route, I would absolutely recommend yoghurt as the way to go.
Yoghurt is very wonderful for you, just doesn’t taste good.
(laughter).
QUESTION. You talked about co-evolution of bacteria with human being,
so like in case of h pylori, it is in developing countries, as you said,
that in developing countries most of the people are infected with the bacterium.
But there is no disease outcome in most of the persons.
So what do you think, is it a pathogen or is it a symbiont?
RICHARD ROBERTS. Okay, so the question relates to helicobacter pylori.
And the fact that most people in developing countries have infections with helicobacter pylori,
most of the infections are relatively low-level,
so you have the organism but you don’t have any serious disease associated with it.
We don’t really know why you suddenly get a disease associated with helicobacter.
In the western world it may be related to diet, it may be related to other organisms that come along.
The incidence of stomach cancer caused by helicobacter pylori are very low in the developing world,
although there are a few cases from time to time, much higher elsewhere.
But I think the real problem is that, as soon as you go from one population to another, the whole microbiome,
the whole set of microbes that are living with you are different.
And so one has to think about not just the helicobacter pylori but all the other organisms that you typically find.
And many of these you simply don’t find in the western world.
And so we have a long way to go.
You know, when you recognise that most of the organisms living with us we don’t know what they are, we don’t know what they do,
it becomes very easy to make hypothesis and much more difficult to test them,
because these are very complicated biota, very complicated environments in which these organisms are living.
QUESTION. My question is how we can fight the multiple drug resistance problem.
Do you think we need to find a perpetual target so that in future we don’t have to look for new antibiotics?
RICHARD ROBERTS. Okay, well, I think the whole question about multiple drug resistance means that we do have to find new drugs
and typically new drugs do not necessarily mean new targets,
sometimes they do, but different classes of compounds that are able to go after a known target but in some different way.
So for instance, if you imagine you’ve got a protein that is really key to the bacterium,
you find a drug that will bind at this point and inhibit it, and so there will be aminoacid changes at the point of interaction.
If you find a different drug that will hit the molecule at some different point in the sequence,
then these mutations won’t affect it and in order for the organism then to become resistant,
it has to make mutations at a different point.
And we know that some of the new drugs that are in the pipelines
just have very different chemical structures from the ones that we’ve already been using as antibiotics.
In some case there are new targets.
And the nice thing about all of the genome sequencing of bacteria that’s taken place over the last few years,
and we have the genomes now for about 500 organisms, there are about another 2,000 or 3,000 that are on the way,
is that there are lots and lots of targets, potential targets that you can find.
So I think there’s no shortage of sort of good targets that one might go after for bacteria,
but there is a shortage of effort to go looking for antibiotics.
You know, in general the drug companies are not very keen on looking for antibiotics
because they have the disadvantage that they cure the disease and so there’s only a small amount of profit for them to make.
The drug companies would much prefer to have something that alleviates the symptoms,
that you have to take for the rest of your life and then you have a very nice profit margin.
QUESTION. Do you believe that with the changing behaviour of human beings,
the pathogenicity of bacteria or any other microbes has either evolved or has even gone down, besides the antibiotic resistance.
RICHARD ROBERTS. Well, you know, we’re in a constant fight between the pathogens that would like to live on us
and cause trouble and our ability to defend against them.
And this is not something that is ever going to go away, you're going to continue to have this evolution,
there will constantly be new pathogens, there will constantly be a need for us to be vigilant, to find ways of dealing with them.
The bacteria have the advantage they in general can evolve very much faster than we are able to evolve.
You know, if you’ve got a 30 minute lifetime, double in 30 minutes, we typically double in,
even in the most favourable situations, every 14 years,
chances of making mutations to accommodate diseases are very much in the favour of the bacteria.
Fortunately our immune system is able to deal with some of these things more effectively,
but there will always be this arms race between the pathogen and the host.
It’s just one of these things, it’s going to happen.
There will fortunately always be a need for microbiologists and for chemists and for scientists
to work in this area and find new antibiotics and find better ways to deal with disease.
QUESTION. Professor, don’t you think that some of the normal organism, for instance which live in the oral cavity,
when there are lowered immunity states, they become pathogens.
So why do you think that happens and how can antibiotics sort of overcome that or play a role in that.
RICHARD ROBERTS. So the question really is, when we’re in a state of lower immune resistance to things,
does this allow pathogens to become much more pathogenic if you like.
And the answer is that whenever an organism becomes pathogenic, it just means that it’s able to grow and you can make lots of it.
Provided you just have low levels of a pathogen, typically they don’t cause problems.
This is why you can sit next to someone who has influenza or tuberculosis, provided you don’t get a significant dose of it,
then your own immune system is typically able to take care of it.
And so it’s really usually a question of the quantity of the organism that is produced.
If you just keep it at very low levels, it’s not pathogenic, you don’t have any severe symptoms.
On the other hand, if it grows to large levels because it’s not being contained,
then you can get all of the symptoms of pathogenicity.
And very often what happens is that as soon as you reach this critical point where you’re making a lot of the organism,
it’s dividing rapidly.
That will then compromise the body’s ability to mount an effective immune response.
And this is what happens in the case of say cholera for instance.
So low levels of vibrio cholerae are fine, but as soon as the organism starts to divide, the body just can’t keep track of it
and can’t keep pace with it, our immune system is not good enough to hold really large quantities of the organism.
Once again, thank you Richard for this wonderful exposé.
(Applause).