SOLS Podcasts

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Peggy Coulombe: Hi! This is Peggy Coulombe with the School of Life Sciences, and this is "Science Studio". Today our format's going to be a little different, as we have two guests.

We have Lynda Williams, who's a geochemist, and an associate research professor from the School of Earth and Space Exploration, and her work largely focuses on the chemistry and structure of clay minerals.

We also have with us Shelley Haydel, a microbiologist and an assistant professor with the School of Life Sciences, and a researcher in the Center for Infectious Diseases and Vaccinology at the Biodesign Institute at ASU. Her research has largely centered on studies with the infective agent of tuberculosis.

Welcome!

Lynda Williams and Shelley Haydel: Thank you, Peggy.

Peggy: You might be wondering, as listeners, how these two individuals with such vastly different research interests are participating in this show. What kind of work could they possibly be doing together? When, in fact, though they are working in very different areas of research, they're actually collaborating on a very exciting project. They're investigating the antimicrobial properties of clay minerals, which, if all goes well, might represent a new avenue for treatments of diseases.

But before we get into the details of your novel research, I'd like to ask you, Lynda, to tell me something about clay. What kind of properties do they have?

Lynda: Well, most people know clay as the sticky stuff that sticks to the bottom of your shoes when you're hiking or gardening. And, in fact, clays are nanoscale minerals. They have a crystal structure. Their structure is like a sheet, a silicate sheet structure that is in layers, so it allows water in between the layers so the sheets can actually slide past each other, making that slippery feeling.

Clays have been used by people since recorded history as poultices for various ailments, and they even eat it to soothe their stomach problems. Kaopectate is one of the common antacids that uses clay to soothe the stomach.

Clays are used in spas and cosmetics, because they absorb oils and organic substances from the surface of the skin, to clean it, and clays hold heat better than water, so, in thermal spas, it's more relaxing.

But clays are highly variable in their structure and their chemical makeup. Their characteristics are as variable as personalities of people.

Peggy: Which is saying a lot.

Lynda: Yes! And some clays, for example, have two silicate sheets bound together, face to edge surfaces, making contacts that are very strong. And these are used to make ceramics, such as kaolinite.

Other clays have the structure of a peanut butter and jelly sandwich, where two silicate units are like the bread, sandwiching cations that stick to the surface of the silicates like the peanut butter, or a more fluid layer of water and molecules that are like the jelly.

So, there are different kinds of clays, and the chemistry of the clays can be as variable as their structures.

So people commonly think of clay as dirt. Therefore, it's something they wouldn't want to put in a wound. But we're finding that there are some clay minerals that actually kill bacteria.

Peggy: Well, Shelley, before Lynda approached you to collaborate on this study of clay as a microbial agent, your research really didn't have anything to do with clay or any other kind of minerals. You primarily focused on tuberculosis and other pathogenic diseases.

Can you tell me something about the infectious-disease-related global health challenges that exist today and about your tuberculosis research specifically?

Shelley: I think you can sort of break down some of the global health challenges that are related to infectious diseases as four different categories. The first one being that we need to be able to create new vaccines for infectious diseases that we currently don't have effective vaccines to prevent.

Secondly, we need to improve the existing vaccines that we actually do have, particularly childhood vaccines, in order to enhance the ability to protect the vast population across the world.

Thirdly, we need to be able to discover new therapeutic agents, or new drugs, to combat multi-drug-resistant microorganisms which are ever-present and problematic these days. And also to prevent diseases or to treat diseases for which we don't have any known therapeutic agents at this time.

And fourthly, and probably most importantly, is to be able to make these drugs and vaccines readily affordable and accessible to all people in both developing and developed nations.

So, up until now, my research has primarily focused on tuberculosis, as you stated. This project is basically performing basic molecular biology research aimed at understanding how the bacterial pathogen that causes TB is able to cause disease in humans.

So if we think about some of the statistics released by the World Health Organization, tuberculosis was declared a global health emergency in 1993 by the WHO, and with approximately one-third of the world's population infected with TB, approximately seven million new cases of active tuberculosis disease a year, and with approximately two million deaths per year, this global health emergency definitely still does exist. It definitely still is global-health challenging.

So we're trying to investigate specific regulatory proteins that are known as two-component regulatory signal transduction systems that have been shown in numerous bacterial pathogens to be important in virulents, or the ability of these organisms to cause disease.

So what we're interested in doing is determining when these systems function, how they function, and how they are able to be involved in the pathogenesis of TB in order to cause disease in humans.

So, at this point, we actually do know that two of these regulatory systems are absolutely essential for growth of M. tuberculosis, and that when you delete the genes from M. tuberculosis, take those genes out of the cell, the bacteria dies. So they're not able to exist without these two particular systems. And since these proteins are essential for microbacterial growth, they would be ideal proteins to target for therapeutic agents.

Additionally, they're conserved across nearly all pathogenic bacteria, and so what we might have on our hands are proteins that could be good targets for, possibly, new broad-spectrum antibiotics.

Additionally, if we're able to generate mutations in some of these regulatory systems in which we can make mutations, if they are unable to cause disease in humans and/or animals, particularly animals at this point, we might be able to improve our vaccination strategies and perhaps collaborate with other groups in order to incorporate some of these mutations in current vaccine strains that are being studied.

Peggy: So, Lynda, how did you feel that Shelley's research strengths and experiences could be instrumental to this project?

Lynda: Well, I started this research in 2002, and I was working at that time with a geological microbiologist, and all we could work with was E. coli, a very common strain of bacteria. Once we found that this particular clay kills the E. coli, we realized that we really needed somebody with a medical background or clinical expertise in microbiology, and Shelley had that. It was just ideal that she had just come to ASU at the time that I was ready to start working on different bacteria, with pathogens that you need special clearance to work with.

So, that, and the fact that she studies tuberculosis, which is related--it's a microbacterium--related to the disease that we were studying.

Peggy: And so the two of you have received a grant for two years from the National Institutes of Health to specifically look at this presumed antibacterial activity of the two French clays on the diseased Buruli ulcer. And you just mentioned the disease briefly.

Shelley, can you tell me something more specific about the disease?

Shelley: Well, Buruli ulcer is a disease that is caused by an infection by a bacterium known as Mycobacterium ulcerans. And this particular organism is closely related to the diseases tuberculosis and leprosy. It's in the same family of diseases. However, the infection is greatly different from what you would see with tuberculosis and leprosy.

Infection with Mycobacterium ulcerans generally leads to extensive destruction of tissue. Skin cells, adipose, or fatty tissue, below the surface of the skin, and the formation of large ulcers that are usually on the legs or the extremities, sometimes the arms as well.

Initially this infection starts as a small nodule, which is basically like a small pimple, if people want to relate it something they might understand. But as the infection continues to grow and spread under the skin, usually what are formed are these large ulcers that have very defined or undermined regions around the ulcer.

The really interesting thing about this particular infection is that it is immunosuppressive; there is basically no pain and no fever that is often associated with these infections.

And that is problematic for a number of reasons. Oftentimes the patients that this particular disease infects, they don't seek treatment because it's a nodule that can be somewhat non-discriminate; but once it becomes ulcerative it doesn't hurt, so they don't seek out treatment, the premise is maybe it will go away.

The problem with that is that the only time we can actually treat this particular infection with antibiotics is when it is in its nodule stage. So if it advances to an ulcerative lesion, we cannot treat it with antibiotics anymore.

There have been several studies where treating the infection at the pre-nodule or the nodule stage with two different antibiotics that are used to treat tuberculosis is effective. However, where we are seeing most of the problems, they don't seek out this treatment.

The other interesting thing about this particular infection is that it's one of the only mycobacterium that we know that makes a toxin. This toxin is known as mycolactone, and is often believed to be the responsible agent for it being immunosuppressive. So the immune response isn't activated, and basically the body doesn't know that this infection is occurring. So that is problematic, and also not having the patients actually seek out treatment.

As I mentioned, at the pre-nodule or nodule stage it is able to be treated somewhat variable with antibiotics, two particular antibiotics, rifampicin and streptomycin.

However, once it becomes ulcerative the only known treatments, if you want to call them treatments, would be surgical excision of that ulcerative lesion, no matter how large it is; and often that surgery requires the excision of healthy tissue that is adjacent to the ulcer.

The second accepted treatment would be amputation. So if we want to consider those treatments, then they are what it is, and those obviously are not the most ideal treatments, particularly for where this disease is problematic.

Peggy: Where is this disease typically found?

Shelley: There have been cases that have been reported primarily in Western and Central Africa, also Australia, Asia, parts of South America. It problematic in Peru and some parts of Mexico.

Since 1980 we have really seen an increase in numbers in Western Africa, and that is where the French humanitarian that we are going to talk about in a brief moment actually performs some of her work, in Western Africa.

Peggy: But it's not in this country.

Shelley: It's not in this country.

Peggy: It's not in the United States. But we will talk more about how the kind of research you are doing can have application in developed countries and the United States as well.

Shelley: I think it's also important to make note that in 1998 the World Health Organization actually did declare this an emerging global health problem, and in 2004 they actually did designate it as a global health emergency. And the World Health Assembly actually did adopt a resolution in 2004 trying to promote research to try to understand the bacterial infection and to promote control, and actually start really documenting and getting some information on surveillance.

Because we have no idea the total numbers of this disease that exists out in the population, because the places where this exists, they don't have good reporting agencies. So the World Health Assembly is really trying to get involved in trying to actually get accurate numbers for how bad this disease actually is, and to draw attention to it.

Peggy: So, Lynda, you were the first person contacted about the clays and about this disease, and I understand that the Internet played some role in that.

Lynda: Yes, the way it came to my attention was that I am a member of the Clay Mineral Society, and we have a list-serve.

The people that observed the healing properties of the clay were working on Buruli ulcer in the Ivory Coast of West Africa. It is a family from France called the Brunet de Courssou family.

The mother of the family was the one who had, for ten years, tried French clays on these people infected in the tribes of Ivory Coast. And she photographically documented healing these people over time.

In two to three months of applications of the "French green clay," she called it, healed these people. She tried other clays that didn't do any healing, so she was convinced that these clays from France had a special property that allowed healing.

Peggy: So none of the clays that are found in the Ivory Coast area had an effect?

Lynda: Correct. Well, Thierry, her son Thierry Brunet de Courssou got on the list-serve to try to find scientists that could help them understand what is the property of these clays that is special.

The reason being that he had gone and presented their results to the World Health Organization to try to get funding to treat the people in the Ivory Coast. It costs only 50 cents a day to do the clay poultice treatment, and they thought this would be a very inexpensive, accessible treatment for these underdeveloped countries.

Peggy: I would have thought the World Health Organization would have jumped at the chance.

Lynda: However, they can't do that until there is scientific validation of why this is killing the bacteria. So he was just trying to find any scientists worldwide that would help them study the problem.

And his idea was that the clay's structure was like a fine fiber or scalpel, nano-scalpels he called them, and that maybe it was stabbing the cells and killing them that way. He just wanted somebody who had the instruments to look at the clays and see what their structure was.

Initially everybody ignored the email that he sent about this Buruli ulcer. And about six months later he wrote another posting saying "Well, I guess no American scientists are interested in helping third-world country people with this problem." And at that point I just thought, "Well, I don't have funding or expertise in this at all but I do have access to a high-resolution scanning electron microscope, so I could take some pictures for him, and that wouldn't take very much time."

So I contacted him and said that I'd be willing to look at his samples at high resolution. So from there they flew me out to their chateau in the Loire Valley of France, which wasn't too hard to take. And I heard all the stories of the healing clays and saw all of the pictures of this process of healing with clays, and got samples of the clay to begin research in testing them against various bacterial populations.

Peggy: And the clay comes in the form of a fine green powder?

Lynda: Yes, and it's sold online as a, I guess they just call it green clay. You can buy it from various healing-clay places.

But, it turns out in our studies that there were actually two clays that are green clays from France. And these clays are a combination of different clay minerals; there is illite-smectite, which is the peanut butter and jelly structure that I talked about; kaolinite, chlorite, and other minerals, calcite and quartz and feldspars in these samples.

The two clays that Line Brunet de Courssou used for healing are mineralogically identical, but chemically, in the trace element chemistry they are not identical. It turns out that one of the clays, the first clay that she would put on the wounds, actually increased bacterial growth.

Peggy: Well that seems counterproductive.

Lynda: Yes, but she didn't know this, all she did was observe. And what she observed was that the bacteria or the infection oozed and got rid of all the dead flesh and tissue, and then the clay began to damage the skin around the wound. And so she switched to what she called a milder clay. It was just a clay from a different supplier that she thought was the same, but she had observed that it had a different property.

And when she put that on, that's when the skin began to granulate and the wounds healed over with nice, soft, supple scarring at the end, instead of hard grafting.

Peggy: So you told me initially. I think Shelley mentioned initially, that there was no pain or that kind of quality of life effect, anyway, when the infection was active. But my understanding is, from the conversations that we've had, that once the clay is put on, that people start to experience pain. What do you think is the root cause for that?

Lynda: Well, her observations were just that, that they had no pain, but huge sections of their flesh were missing, down to bone and muscle. When she put on the first clay, initially it caused a terrible odor and lots of oozing. And they described the pain as excruciating, as equivalent to, perhaps, childbirth.

But that went on for just a few days.

After that phase, I think that's when something was attacking the mycobacterial infection. Then she'd switch to the other clay, and everything was fine. They would be in this treatment for several months, but they didn't have months of pain, just a few days.

Our working hypothesis at this point is that the first clay that actually increases bacterial growth, may have awakened the immune system response, and the body was actually killing the mycobacteria along with other bacteria that may have been growing in the wound.

Then when she put on the second clay that we have found kills bacteria, maybe it killed all of the bacteria that were in there and allowed healing to take place. We're still investigating the mechanism, though. We don't know that.

Peggy: So you don't know what causes the activity, the antibacterial activity.

Lynda: Not yet. We have some good clues. We've done a lot of research. Basically, it's like a detective story. You have clues. We're eliminating a lot of possibilities, and so we know what doesn't cause the antibacterial behavior. We're honing in on what it is.

Peggy: So, Shelley, how effective is the clay? What kind of organisms has it been tested on?

Shelley: Well, initially, as Lynda had stated, the initial work was done with just basically a laboratory strain of Escherichia coli. They did show, in 2002, that in that particular strain of Escherichia coli, that growth was inhibited.

When I got involved in this particular project, I wanted to approach it more from a clinical microbiologist's standpoint. So all of the bacterial strains that we're actually using to determine if these particular clay samples are able to kill the bacteria, are the same bacterial strains that pharmaceutical companies use to test their antibiotics, and also to perform just generic, ordinary, quality control activities with their antibiotics.

So from that sense, we're definitely approaching it from more of a medical standpoint. So what we've actually shown is that one of the particular clay samples, similar to what Lynda was just describing, actually does kill a large number of pathogenic bacteria.

Some of the bacteria that we have tested that we see complete killing with is Escherichia coli. People might relate Escherichia coli, E. coli, to the Jack in the Box outbreak from years ago. If we need to link it to something.

Salmonella typhirium, which causes gastroenteritis. It kills it completely. Pseudomonas aeruginosa, which can be problematic in a number of different people, mostly immuno-compromised patients.

It partially kills Staphylococcus aureus. But it also partially kills Methicillin or multi drug resistant Staphylococcus aureus.

So that gave us some good information, in that we believe that however the clay is inhibiting growth, or inhibiting some of the growth, is different than the current antibiotics that we actually do have.

We've shown that it's able to completely inhibit growth of Mycobacterium marinum, which is closely related to Mycobacterium ulcerans, in that it causes a skin infection, but it's not nearly as devastating as Mycobacterium ulcerans.

But genetically, and evolutionary linkage to Mycobacterium ulcerans, M. marinum is the most closely related.

So that gave us some exciting data, to say that if we're able to cure Mycobacterium marinum, chances are we're going to be able to actually see killing of Mycobacterium ulcerans.

The one thing about Mycobacterium marinum, is that it's a relatively faster growing Mycobacterial strain, in that we can do these experiments usually in about two weeks.

To do all the experiments with Mycobacterium ulcerans is going to take us about six months, to do one particular trial. We have actually done one series of experiments with Mycobacterium ulcerans, and from that particular experiment, we don't see 100 percent killing. But we see approximately a 40 log, or a 40-fold, reduction in the level of growth. So it definitely is inhibiting growth of Mycobacterium ulcerans.

Those experiments will be performed within the next year or two, to actually validate those experiments.

Peggy: Why does it take so long? The series of experiments take six months with the Mycobacterium ulcerans?

Shelley: Mycobacterium ulcerans, its ability to replicate one cell into two cells, is quite a long time. It takes days to do that. If you think about Escherichia coli, in an optimal situation, which is what we try to give it in the laboratory, it takes E. coli 20 minutes to replicate from one to two bacteria.

So if we're looking at days for one cell to become two, we're trying to look at it over at least a month of exposure to the antibacterial clays in order to see if it is going to be killing.

Then we have to do the plating assays, and then we have to let that grow. So we're looking at about a total time, if everything works perfectly, of five to six months.

Now, additionally, if we look at the other clay mineral that Line Brunei de Courssou actually used, we actually see that that particular clay mineral promotes the growth of bacteria. We see it promoting, at a slight level, E. coli, a little bit, Pseudomonas aeruginosa. We're basically not seeing any change in growth characteristics of those bacterial strains in the presence of that particular clay.

And Lynda could probably tell you a little bit more about the chemistries of the clays, those two particular clays, but they are very, very similar. And so here again, that's the clue-based search that we're trying to become involved with in this adventure, is to try to pinpoint specific differences, and there are very few of them.

Peggy: Yeah, that was my next question. With the two clays being quite similar in elemental composition, what it is about them that makes them so very different in the way that they affect the mycobacterium, potentially?

Lynda: That's our research. That's what we're just starting to do, is to figure out what is the component, or magic ingredient, in one that promotes bacterial growth, while the one that's mineralogically identical, kills the bacteria?

Our initial thoughts were, these are green clays, so they probably have reduced iron in them. And in fact, they have about six weight percent iron in both of them. And so that's unusual. And we thought we would look at whether it was the iron, or properties of the oxidation state of the mineral, that had to with the bacterial impact.

But we've changed the oxidation state of the clays and actually found that they kill even better as they're oxidized. We've destroyed various layers of the structure of the clay and found that that doesn't change their killing properties.

But what does is when I chemically remove all of the cations, all of the jelly layer of the peanut butter and jelly sandwich, when I remove those then it no longer kills. So that tells us that there is something bound to the mineral in those sites that is probably responsible for killing the bacteria.

So we're investigating further what that chemical, or chemicals, could be.

Peggy: So remind me. I asked a little bit earlier about the chemical structure of clays and how they are formed. How does the water enter into a clay, and what can make it so different, this liquid layer?

Lynda: Well the unique thing about clays, unlike crystal, like quartz, that is three-dimensionally solid, it has exterior surfaces that you can hold in your hand, clays are sheets that can extend over large areas. So the surface area of the clay is very large and it has a negative charge on it, so it attracts cations to the surface.

The layers of the clay then are attracted to each other by very weak forces, and that allows water to go in between the sheets of the clay so that the clays can expand, and it can incorporate cations and molecules, even organic molecules.

Whatever is in the water can be incorporated into the clay, and if it finds a bonding site that fits its size and charge then it's happy to sit there and be retained in the clay even after you dry out the clay.

But it is basically the large surface area of clays and the fact that they occur in sheets that are expandable that makes them absorb the chemicals in the water around the mineral. And that's why I think the one particular clay was grown in a different chemical environment than the other one that was similar but doesn't have the same effect.

Peggy: And when you talk about growing, I mean I never thought about clay as a growing...

Lynda: As a growing thing?

Peggy: Yeah.

Lynda: Well, minerals precipitate on surfaces just when all the components that are needed to form a mineral, the silicon, aluminum, magnesium, iron, oxygen, are there, and the pressure and temperature are right, they will precipitate from solution.

And so they precipitate as small crystals and incorporating all the chemicals from that environment. And over time, over, we're talking millions of years; they will grow and incorporate the chemistry of the waters that are present as they grow. So the chemistry can change with crystal size.

And that is one of my research topics, is how does a clay mineral change in its chemistry and isotope properties with crystal growth, so that we can record past conditions by looking at a clay that is present today.

Shelley: So it's certainly a different type of growth than I deal with.

Lynda: It's not biological growth.

Peggy: Not biological growth.

Lynda: You know, imagine precipitating something in it, like salt crystals, and they get larger and larger.

Shelley: I think it would be a good idea for you to touch on, we talked about the chemical differences with the two different clays, but we might not just be able to find a specific chemical, and you made statements that it might actually have to be complexed with these clays, and that might be involved.

Lynda: Yes, and what we don't know yet is if it is the clay delivery of whatever the chemical is, is important. Because if we can find, for example we'll find a transition metal that is toxic to the bacteria, if we just put that in the water would it do the same thing or is it really the clay surface and the delivery of the chemical by the clay that is important. We don't know, and those are things that we will be testing.

Peggy: Sounds like a really great mystery novel, and you've got a few chapters yet to work on.

Lynda: Oh yeah.

Peggy: Shelley, how do you think this kind of research can play a role in controlling infectious diseases in developing countries?

Shelley: Well it's obvious that just listening to the story and listening to where this particular disease is problematic obviously ties it to infectious diseases in developing countries, considering that it is problematic in many parts of Africa, Central and West Africa.

I mentioned about the World Health Organization trying to target this particular disease and make it be known that it is a global health threat, and the World Health Assembly addressing the need to provide better surveillance and better control and better research efforts.

But I think if we can actually start to understand the mechanism by which these natural clay minerals are inhibiting bacterial growth, and how it actually was allowing these patients with Buruli ulcer to heal, then we've potentially identified a substance that acts as a therapeutic agent that, one, is a naturally available resource, two, that can be applied topically, and three, that it has very few special handling requirements.

So one of the things that we are looking for as far as drugs or therapeutic agents in many of these developing countries is that it doesn't require refrigeration, any type of special handling related to that. And it's not something that needs to be injected, so you are not trying to have needles and syringes, which obviously brings in different things to think about. And so for those reasons this would be a great product to develop for developing countries.

Peggy: Did either of you think about doing collaborative enterprises with people in such different fields? I mean, I'm sure you've done collaborative work with people within your fields, but this is taking you in really new directions. What did you learn from participating in this study together?

Lynda: Well, it's fun working outside of your specialty.

And I think that Shelley would agree that what we've really learned is how ignorant we are when we step out of our own specialty. And that's what gets scientists turned on, because if there is a process that we don't understand, then we are especially driven to find out how it works.

So by leaning on each other's expertise we can make rapid progress toward our goal of learning this process without understanding, necessarily needing to know all of the background that would have taken us years to learn on our own. So it speeds up the progress to answering the fundamental questions.

Peggy: So I understand that some traveling is in both of your futures here, off to France I think. Will you be taking a hot springs excursion while you are there?

Shelley: Well actually I don't know about the hot springs excursion, but...

Lynda: It's December!

Shelley: It's December, so we might need to get into the hot springs.

But we are planning to travel to France, December 8th through the 15th, in order to go meet with the people that own the factory where the one particular clay that we have actually shown antibacterial properties of that particular clay mineral. We plan to meet with the scientists there and the owner of the company, and present our research to let them know what we are doing, and to hopefully get them involved, and also to bring back additional samples, or to ship those samples back to us.

Lynda can probably talk a little bit more about her interest in going to the mountainous region of France in order to investigate geologically the mining sites in that particular region where these clays are mined.

Lynda: Yes, we, unfortunately, have been given these two clays that this woman used in this process on the Ivory Coast, and my interest is in the geologic environment in which they formed.

So we have to know that, and we can guess a little bit from the mineralogy and the chemistry what type of environment they formed in, but we really, since they are so mineralogically similar, we need to go to the mine, the original geologic source where this antibacterial clay is found and see what is different about that geologic environment from the source of the other green clay that promotes bacteria. So geology is really important and that is part of my reason for wanting to go to France to find the source.

I think that there are probably lots of antibacterial clays in the world. No one has looked for them or people just assume that all of them will do the same thing, and as I said, they are as different as people's personalities. And we need to find out the characteristics that are similar and track down more of these clays to adequately understand them, how they grow, what their chemistry is, and how they can be used in healing.

Peggy: And possibly how to develop your own artificial clay?

Lynda: Well, of course the end goal then would be once you find the natural sample and understand the mechanism, and then we can synthesize clays and probably would be able to synthesize a substance that would behave like this natural product.

Peggy: Well I wish you both lots of luck in your research. It's been a pleasure interviewing you today, and thanks for your time.

Shelley: Thank you Peggy.

Lynda: Thank you.

Antibacterial clay, a new medical frontier?

Transcript - [Printable PDF format]

SOLS Podcasts 2007