'Bacillus anthracis and Anthrax': The past, present and future of anthrax research

'Bacillus anthracis and Anthrax': The past, present and future of anthrax research

Few strands of bacteria have achieved such a central place in public consciousness as Bacillus anthracis, the bacteria which causes Anthrax. While today it is a feared weapon of bioterrorism Bacillus anthracis has played a significant historical role, especially through the research of the celebrated 19th century scientists Robert Koch and Louis Pasteur, in shaping our understanding of infectious diseases and immunology.

In his new book Bacillus Anthracis and Anthrax Dr Nicholas Bergman brings both of these perspectives together to present a definitive 'state of the field' summary for anthrax research, providing a comprehensive guide to all aspects of the organism, ranging from basic biology to central public health issues.

"With all the attention and research that have been focused on Bacillus anthracis and anthrax in recent years, our understanding of both the organism and the disease has improved dramatically," said Bergman. "This book aims to provide a up-to-date reference that will be useful to scientists, medical and public health personnel, and those playing roles in shaping public policy."

Bacillus Anthracis and Anthrax covers all major aspects of Anthrax biology, from basic biology and pathogenesis to diagnosis, treatment, and prevention of anthrax bioterror-associated issues.

Throughout the book anthrax is considered historically as well biologically, with chapters ranging from the impact of anthrax on human history from 5000 BC by Peter Turnbull and Sean Shadomy, to an assessment of current anthrax vaccination research by Elke Saile and Conrad Quinn, as well as an analysis by Leonard Cole of anthrax as a weapon of war.

The biological analysis of B. anthracis, includes research on life cycle, differentiation, cellular structure, as well as the interaction of B. anthracis with the immune system.

Bacillus Anthracis and Anthrax also considers the clinical features, diagnosis and treatment of the different forms of human anthrax, as well as a review of animal models of anthrax and their use in research.

While Bacillus Anthracis and Anthrax will be a premier reference tool to B. Anthracis and anthrax for microbiologists, immunologists and physiologists it will also serve as an invaluable resource for medical professionals, bioterror experts and all those involved in the issues of public health.

Researchers ID molecular link key for cell growth

Researchers ID molecular link key for cell growth

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Images of yeast cells expressing fluorescent proteins. Microtubules (part of the cytoskeleton) are shown in green and the lipid PI4P in red. The white arrows here denotes the direction of the cell growth.

(PhysOrg.com) -- When a cell is preparing to grow or replicate, it starts the way a monarch planning to expand his territory might: by identifying and marshaling the necessary resources, loading them onto the appropriate vehicles, and transporting them to the front line.

For cells, that means connecting key molecules with so-called motor proteins, which are neatly equipped to recognize them and carry them to their designated positions at the intended site of growth.

In research published Jan. 18 in Developmental Cell, Cornell scientists report on two molecules that work together to initiate that process in yeast cells. The research is a step toward understanding how cells orient themselves within their surroundings and, ultimately, toward finding new ways to fix the process when it goes awry.

In yeast and other organisms, membrane-bound organelles known as secretory vesicles and other compartments are responsible for providing membranes needed to build another cell. In the current research, Anthony Bretscher, professor of molecular biology and genetics, graduate student Felipe Santiago-Tirado and colleagues studied how the motor protein myosin-V, which transports secretory vesicles along filaments of the cytoskeleton, recognizes and binds with its appointed cargo.

They found that two key molecules -- the protein Sec4 and the lipid PI-4P -- work together to facilitate the selection and binding. By requiring two molecular indicators rather than just one, the researches say, cells can closely regulate the cascade of processes that lead to cell growth.

The findings also demonstrate that lipids, normally thought to be just simple barriers, can play a vital role in molecular processes.

An image from a movie of a yeast cell expressing a marker for the lipid PI4P. Multiple frames where superimposed to illustrate the directed movement of a PI4P rich compartment towards the growing bud. The compartment starts at the bottom and one second later is at the top of the cell.

To understand the process, the researchers used confocal microscopy to observe genetically modified yeast cells in which the key protein and lipid molecules were visualized with green fluorescent proteins.

They then tested the cells' ability to grow under a variety of conditions. "By looking at both the lipid and protein markers at the same time, we found that the lipid co-localized with specific proteins and not with others. And it turns out that the ones that co-localized with the lipids are the ones that are associated with secretory compartments," said Santiago-Tirado, who led the study.

If the lipid was present without the protein, or vice versa, the myosin-V protein still trundled along its path to the site of growth -- but with no secretory vesicle attached. "It recognizes these cargoes through both binding a protein, and indirectly through binding a lipid," said Bretscher. "So it's actually a coincidence detector -- it has to bind both."

By greatly boosting either the protein or the lipid when the other element wasn't present, the researchers were able to prompt some cell growth; but the new cells were far less robust.

The research is a step toward deciphering the way cells organize their structure and respond to changes, Bretscher said. The same type of mechanism is likely to apply in mammalian cells, he added.

An image of yeast cells expressing fluorescent proteins. The proteins localize to specific parts of the cell, specifically the areas undergoing active cell growth. The secretory vesicles are in green and the plasma membrane in red.

The work also suggests the need for further studying the role of lipids in cellular processes, Santiago-Tirado said.

"Proteins have been shown to play a role in many things in the cells, but lipids were thought to be just a physical component of the membrane and not involved in this process," he said. "But here we show that lipids also are important -- they do something by themselves."

Ultimately, the findings could lead to treatments for a variety of diseases, Santiago-Tirado said.

"Many diseases are related to the failure of moving these components; so if we understand how the myosin binds to the cargo, then maybe we can try to fix a condition where the myosin is unable to bind to the cargo."

The research was funded by the National Institutes of Health.

Human embryonic stem cells in culture created

Human embryonic stem cells in culture created

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Human embryonic stem cells in culture created by UCLA researchers

(PhysOrg.com) -- In regenerative medicine, large supplies of safe and reliable human embryonic stem (hES) cells are needed for implantation into patients, but the field has faced challenges in developing cultures that can consistently grow and maintain clinical-grade stem cells.

Standard culture systems use mouse "feeder" cells and media containing bovine sera to cultivate and maintain hES cells, but such animal product–based media can contaminate the cells. And because of difficulties in precise quality control, each batch of the medium can introduce new and unwanted variations.

Now, a team of stem cell biologists and engineers from UCLA has identified an optimal combination and concentration of small-molecule inhibitors to support the long-term quality and maintenance of hES cells in feeder-free and serum-free conditions. The researchers used a feedback system control (FSC) scheme to innovatively and efficiently select the small-molecule inhibitors from a very large pool of possibilities.

The research findings, published today in the journal Nature Communications, represent a major advance in the quest to broadly transition regenerative medicine from the benchtop to the clinic.

"What is significant about this work is that we've been able to very rapidly develop a chemically defined culture medium to replace serum and feeders for cultivating clinical-grade hES cells, thereby removing a major roadblock in the area of regenerative medicine," said Chih-Ming Ho, the Ben Rich–Lockheed Martin Professor at the UCLA Henry Samueli School of Engineering and Applied Science and a member of the National Academy of Engineering.

Unlike current animal product–based media, the new medium is a "defined" culture medium — one in which every component is known and traceable. This is important for clinical applications and as drugs or cells enter the world of regulatory affairs, including good manufacturing practice compliance and Food and Drug Administration supervision.

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Representation of the feedback system control scheme used by UCLA researchers to identify an optimal combination and concentration of small-molecule inhibitors to support the long-term quality and maintenance of hES cells in culture. (Image credit: UCLA)

"It is also the first defined medium to allow for long term single-cell passage," said the paper's senior author, Hong Wu, the David Geffen Professor of Molecular and Medical Pharmacology at the David Geffen School of Medicine at UCLA and a researcher with UCLA's Eli and Edythe Broad Center of Regenerative Medicine and Stem Cell Research.

Single-cell passaging — a process in which hES cells are dissociated into single cells and subcultured through single-cell–derived colonies — is important in overcoming the massive cell death associated with hES cell dissociation during routine passage, and it allows for genetic manipulation at the clonal level.

"Although other studies have demonstrated growth of hES cells under defined media formulations and/or on defined surfaces, to the best of our knowledge, this is the first study that combines defined cultures with routine single-cell passaging, which plays an important role in supplying a large mass of clinically applicable cells," said Hideaki Tsutsui, a UCLA postdoctoral scholar and lead author of the study. "Thus, our hES cell culture system, guided by the FSC technique, will bring hES cells one step closer to clinical therapies."

Initially, the very large number of small molecules in the culture medium and their unknown synergistic effects made it difficult for researchers to assess the proper concentration of each for achieving long-term expansion of hES cells. The major challenge was to find the best way  to sort out those molecules and rapidly determine the best combinatorial concentrations.

The breakthrough, ultimately, was the product of a close interdisciplinary collaboration.

Tsutsui, then a UCLA Engineering graduate student, and Bahram Valamehr, then a graduate student at the Geffen School of Medicine, started working on the project two years ago. Armed with biological readouts and analyses of stem cells mastered in Hong Wu's laboratory through the lab's extensive accomplishments in stem cell research, Tsutsui and Valamehr used the FSC scheme — developed previously by Ho's group to search for optimal drug combinations for viral infection inhibition and cancer eradication — to facilitate the rapid screening of a very large number of possibilities.

Working together, the team was able to discover a unique combination of three small-molecule inhibitors that supports long-term maintenance of hES cell cultures through routine single-cell passaging.

"There are certain research projects biologists can dream about, and we know we can eventually get there, but we don't have the capacity to achieve them in a timely manner, especially in a study like this," Wu said. "It would have taken 10 graduate students another 10 years to test all the possible combinations of molecules. Having an opportunity to collaborate with the engineering school has been invaluable in making this dream a reality."

"This is the best example of demonstrating the strength and potential of interdisciplinary collaborations," said Ho, who is also director of the Center for Cell Control at UCLA Engineering and a senior author of the paper. "Engineers and biologists working side by side can accomplish a mission impossible."

Other authors of the study included Antreas Hindoyan, Rong Qiao, Xianting Ding, Shuling Guo, Owen N. Witte and Xin Liu.

Shedding light on the elegant mechanisms that control the push and shove of cells in living organisms

Shedding light on the elegant mechanisms that control the push and shove of cells in living organisms

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Figure 1. a-Catenin and myosin in epithelial cells. a-Catenin (blue) is a protein that forms part of an ?adhesion apparatus? for joining adjacent cells and is uniformly distributed at cell boundaries. Myosin (green) is another protein that produces a force that deforms the inner structure. The areas undergoing the resultant structural change are shown in pink.

The many amazing photomicrographs on display at the entrance to the Electron Microscope Laboratory in the RIKEN Center for Developmental Biology (CDB) were all taken by laboratory leader Shigenobu Yonemura and his colleagues. In addition to its own research program, the laboratory also offers technical assistance with electron microscopic analysis to researchers at other laboratories in the CDB. “Moving cells seem to have a life of their own. I have long been fascinated by the motion force generated by cells,” says Yonemura. His team’s recent clarification of the mechanism by which adjacent cells pull and pull against each other has attracted considerable attention.

Yonemura clearly remembers his days as a graduate student examining the development of the sea urchin. “The fertilized egg of a sea urchin cleaves and replicates, doubling the number of cells in sequence to build up a spherical body. At one point, part of the sphere suddenly sinks, taking surface cells into the body itself. This process is known as archenteron invagination. I was fascinated by the change, in which it looks as if the surface cells move under their own volition. Since then, I have been interested in the force generated by cells.”

That force is produced by two proteins: actin and myosin. Individual actins occur in spherical form, with many actins joining together to form actin filaments. As myosins move on the filaments, a force that pulls the filaments is produced, which in turn allows the cells to move or change their form. “It is not necessary for the cells to be in the process of morphogenesis, such as during archenteron invagination, for them to generate a force. For example, adjacent epithelial cells are constantly pulling at each other.”

Epithelial cells play an important role in separating the internals of a living body from the outer world by arranging themselves in a sheet to form the surface of the skin and the gastrointestinal tract. Adjacent epithelial cells are linked together by adhesion apparatus (Figs 1, 2). The key component of this apparatus is cadherin, a protein discovered in 1982 by Masatoshi Takeichi, director of the CDB. Cadherin penetrates the cell membrane, with one end exposed to the cell surface, and the other end protruding into the cell. Bound to the end of the cell are a-catenin and ß-catenin. As the actin filaments bind to the a-catenin and the myosin acts on the filaments, a pulling force is produced.

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Figure 2. Mechanism producing tensile forces among adjacent cells. Cadherin binds to actin filaments via a-catenin and ß-catenin, forming an adhesion apparatus. When not bound to a nearby cell, myosin does not act on the actin filament, and the a-catenin assumes a bent structure. When cadherin is bound to that in an adjoining cell, it is pulled strongly, inducing myosin to act on the actin filament. As both ends of the a-catenin are pulled in opposite directions, the bent portion of the a-catenin stretches. Vinculin then binds to the a-catenin, causing the actin filament to bind even more strongly to the a-catenin. The adhesion apparatus is thus enhanced, producing a pull-back force. enlarge image

“As cadherin adheres to the same protein in an adjoining cell, the adjoining cell is pulled by tensile force. If that pulling force continues, however, the cell is deformed. A good balance cannot be achieved unless the adjoining cell pulls back. When pulled strongly, the cell pulls back strongly, and when pulled weakly, it pulls back weakly. Believing in the existence of a mechanism behind this, I have been trying to find what it is, and recently succeeded in clarifying it. The key player proved to be a-catenin."

The mechanism is remarkable. Each cell contains a-catenin, which assumes a bent structure (Fig. 2). When pulled by an adjoining cell, the bent portion stretches. The vinculin molecule then binds to the a-catenin, and as the actin filaments continue to bind to the vinculin, the adhesion apparatus is enhanced and a pulling-back force is produced.

“This can be compared to a tug-of-war in which one team is about to lose the game as it is pulled with a strong force by its opponent, then many helpers come to join and pull back strongly,” says Yonemura. When the opponent's pulling force weakens, the helpers are no longer necessary. The a-catenin then bends again, and the vinculin and actin filaments leave the adhesion apparatus, restoring the original state. “From this system, I realized that a-catenin is responsible for two tasks: sensing the forces and enhancing the adhesion apparatus.”

When a cell is pulled by an adjacent cell, it must immediately pull back at the same location. However, transducing information about such a response by the release of a signal transmitter, as occurs in many biological processes, would not provide the responsiveness required to balance rapid changes in pulling location and strength. “It is reasonable that one molecule plays the dual roles of sensing the forces and enhancing the adhesion apparatus. We have arrived at a definite answer to the inveterate problem of how cells perceive forces and respond to them.”

Yonemura is planning to make observations of how the a-catenin structure changes to allow binding to the vinculin, and to quantify the pulling force required to cause morphological changes in the cells.

“Pulling at each other is very important for cells. I think that mutual pulling is utilized in, for example, sensing whether an adjoining cell is alive or dead,” says Yonemura.

Dead epithelial cells are quickly eliminated from the sheet structure. “The mechanism by which cells sense the death of adjoining cells remains unclear. Although it is said that dead cell detection may be achieved by molecular exchanges on the cell surfaces, I do not think that’s the whole story.”

To investigate the mechanism behind the sensing of dead cells, Yonemura artificially damaged epithelial cells and examined them in the process of repair. Similar experiments undertaken before had not yielded good results because the experimentally inflicted damage affected a larger range than intended due to cell scratching. Yonemura succeeded in selectively killing a target cell by laser irradiation. His technique has made it possible to make extensive observations of the behavior of cells adjacent to the dead cell (Fig. 3).

“When a cell dies, a change begins to occur in the cells adjacent to the dead cell. Actin filaments and myosins gather on the surfaces in contact with the dead cell as if they were joining hands to form a ring surrounding the dead cell. The ring gradually shrinks, and eventually the dead cell is ejected from the sheet.”

This accumulation of actin filaments and myosins begins as soon as a cell dies. “The repair of epithelial cells cannot begin immediately as it does unless actin filaments and myosins are involved in sensing cellular death,” says Yonemura. “Cells are constantly pulling at each other. When an adjacent cell has died, however, the living cell in question continues to pull the dead cell, but is no longer pulled back. It is through this process that living cells may sense the death of an adjacent cell. Such a process would ensure that death signals are detected earlier and more accurately, allowing the elimination of the dead cell to start more quickly than if cellular death were detected by molecular exchange on cell surfaces.”

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Figure 3. Elimination of dead epithelial cells. Epithelial cells visualized by transmission microscopy (upper) and fluorescence microscopy (lower) showing intracellular myosin. When an epithelial cell is damaged (center of each plate) by laser irradiation, actin filaments and myosins in adjoining cells gather to form a ring around the dead cell. The ring then gradually shrinks to expel the dead cell out of the sheet. enlarge image

However, that may not be the full story. “When actin filaments and myosins have formed a ring surrounding the dead cell, the forces remain balanced. It is natural that the process ceases in that state. In actuality, however, the ring continues to shrink further to eliminate the dead cell. There must be another, unknown mechanism that breaks the balance of forces. Clarification of the mechanism behind the series of processes from the sensing of cellular death to its elimination is an issue that remains to be addressed.”

Of course, gene expression and molecular signal transduction are vitally important to the functioning of cells. “Although this is true, there is also a wide variety of mechanisms that act like machinery in cells. I am much more interested in those types of machinery. I want to discover these exquisite mechanisms, which are remarkably simple and controlled by feedback,” says Yonemura.

In addition to its own research program, the Electron Microscope Laboratory provides technical support for electron microscopic analysis to researchers at the CDB. Yonemura also provided such support while conducting his own research at the Laboratory for Cellular Morphogenesis in the CDB, for which he served as team leader between 2001 and 2006. Even after the team was renamed the Electron Microscope Laboratory in April 2007, its tasks have continued basically unchanged.

“Only a few researchers are good at using electron microscopes,” says Yonemura. Electron microscopes have a resolution of as fine as 0.1 nanometers, compared with the much coarser resolution of 200 nanometers achievable using optical microscopes, making it possible to observe much smaller features. “It is likely that users realize the performance of the electron microscope but tend to view it as something that is difficult to operate, possibly because of the large amount of instrumentation, so they are reluctant to use it. Myself and two technical staff members provide technical assistance on their use.”

At the Electron Microscope Laboratory, members manage two transmission electron microscopes and one scanning electron microscope, as well as peripheral equipment including two microtomes for preparing sample sections. “We want researchers to be able to examine as many samples as possible, so we chose to install more pieces of standard equipment, rather than one or two highly specialized, high-performance units.”

Currently, the laboratory provides assistance to about 20 research projects annually. In some cases, support is provided for all steps from the preparation of resin-fixed sectional samples to examination and photographic recording. In other cases, it is only necessary to provide instructions on how to use the instruments. Many different types of materials are brought into the laboratory, including mice, drosophila fruit flies, nematodes, zebrafish and chickens. The types of tissue examined are also diverse, and include embryos, nerves and kidneys. “New types of samples can be quite difficult to handle the first time, so it can take a lot of time to prepare them properly. However, since all trial-and-error experimentation represents the accumulation of knowhow, we always endeavor to work steadily without rushing. State-of-the-art techniques are not the only key to success in this field. We must have a broad range of knowledge about the wide variety of tissues of various organisms, and be able to hold scientific discussions with the users.”

When providing support, Yonemura discusses the project and desired goals with the requestor. “We do this to determine whether the target is in fact suitable for analysis using an electron microscope. Electron microscopy only allows a relatively narrow range of examination compared with optical microscopy. The sample must also be fixed in resin, and this is a time-consuming procedure. Our discussions sometime lead us to recommend use powerful optical microscopes. To ensure the best outcomes, we make it a rule to first discuss things in detail with the requestor.”

Yonemura’s support role also has its own benefits. “The support work allows me to get involved in many kinds of research that I would otherwise never do myself, and it provides me with opportunities to see the very latest achievements before they are published. For me, the greatest fascination is in meeting many different people. It makes me very happy to be able to continue to do my own research and at the same time balance that with our support work.”

Skin provides Australia's first adult stem cells for rare genetic disease

Skin provides Australia's first adult stem cells for rare genetic disease

(PhysOrg.com) -- Scientists have developed Australia’s first adult induced pluripotent stem cell lines using skin biopsies from patients with the rare genetic disease Friedreich Ataxia (FA).

The study was conducted by the University of Melbourne and Monash Institute of Medical Research and is published in the current online edition of the international journal Stem Cell Reviews and Reports. It is the first time adult pluripotent stem cells, known as iPS cells have been developed for a specific disease in Australia, allowing for the development of new treatments for FA and related conditions such as diabetes and heart disease.

Induced pluripotent stem (iPS) cells result from the reprogramming of adult cells, such as skin cells, and are similar to embryonic stem cells in that they have the potential to generate any cell type of the body.

Dr Alice Pébay and Dr Mirella Dottori, co leaders of the study from University of Melbourne, characterized and directed the Friedreich Ataxia iPS cells to become specific cell types, including heart cells and nerves, which are normally not functioning well in the disease.
“By focusing on the heart and nerve cell types, we hope to be able to develop treatments to improve heart function and the loss of movement experienced by patients with FA,” Dr Pébay said.

Friedreich Ataxia affects one in 30,000 people globally, and Dr Paul Verma of the Monash Institute of Medical Research said this research could be applied to other diseases.

“Due to the number of symptoms experienced by people with FA, including diabetes and heart disease, this resource could be applied to developing treatment for those conditions and helping even more people, “ he said.

Dr Dottori said the research could not have been achieved without a significant network of experts and support from the Friedreich Ataxia Research Association (Australasia) (FARA-A) and the Friedreich Ataxia Research Alliance (FARA) in the United States.

“It is the collective effort of clinicians, scientists, patients and FARA that has made this discovery possible,” she said.

Ms Varlli Beetham, Executive Director of FARA said the finding provided real hope for people suffering the debilitating condition. “We are proud to have supported this research effort and look forward to the next stage of research, the development of new trial treatments,” she said.

A pesky bacterial slime reveals its survival secrets

A pesky bacterial slime reveals its survival secrets

January 7, 2011

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Slimy bacterial coatings known as biofilms (Bacillus subtilis colony superimposed at center) exhibit an unmatched ability to repel a wide range of liquids and even vapors. An electron microscope image shows the biofilm surface's resilient meshwork made from proteins and polysaccharides and assembled into a multiscale, hierarchical structure. Credit: Courtesy of the laboratory of Joanna Aizenberg, Harvard School of Engineering and Applied Sciences.

By rethinking what happens on the surface of things, engineers at Harvard University have discovered that Bacillus subtilis biofilm colonies exhibit an unmatched ability to repel a wide range of liquids -- and even vapors.

Centimeters across yet only hundreds of microns thick, such slimy bacterial coatings cling to the surfaces of everything from pipes to teeth and are notoriously resistant to antimicrobial agents. The researchers now suspect they know the secret to a biofilm's resiliency.

Published in the January 5th early edition of the Proceedings of the National Academy of Sciences (PNAS), the study holds promise for both creating bio-inspired non-wetting materials and developing better ways to eliminate harmful biofilms that can clog pipes, contaminate food production and water supply systems, and lead to infections.

"By looking at biofilms from a materials perspective rather than a cellular or biochemical one, we discovered that they have a remarkable ability to resist wetting to an extent never seen before in nature," says lead author Alex Epstein, a graduate student at the Harvard School of Engineering and Applied Sciences (SEAS). "In fact the biofilm literally resisted our initial efforts to study it."

The finding came about serendipitously, as the original intention of the researchers was to study the structure of the biofilm. To image the interior of the biofilm, the team had to soak it with liquids such as ethanol and acetone, which normally spread and seep easily into a surface.

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Four drops of ethanol solution placed on a Bacillus subtilis biofilm colony, the light-colored film on top of the sectioned agar gel, bead up instead of readily wetting and seeping in. This macroscopic phenomenon reveals a critical clue to what may be responsible for biofilms' broad antimicrobial resistance. Credit: Courtesy of the laboratory of Joanna Aizenberg, Harvard School of Engineering and Applied Sciences

"But to our surprise, it was impossible. The liquids kept beading up on the surface and wouldn't infiltrate the colonies," says Epstein, who is a member of the laboratory of Joanna Aizenberg, Amy Smith Berylson Professor of Materials Science at SEAS; Susan S. and Kenneth L. Wallach Professor at the Radcliffe Institute; and a core member of the Wyss Institute for Biologically Inspired Engineering at Harvard.

As the Aizenberg lab studies materials and wetting, the engineers immediately recognized the significance of what they were observing. It turns out that biofilm has an unprecedented liquid-repellent surface, thereby revealing a critical clue to what may be responsible for its broad antimicrobial resistance.

Nature offers numerous examples of water-resistant surfaces, such as the lotus leaf, a longstanding inspiration for creating synthetic materials. Until now, however, no model natural systems have been found for broadly repellent materials.

While such surfaces can be manufactured, the top-down process is costly, labor intensive, and reliant on toxic chemicals and brittle structures. A biofilm, however, is living proof that only the simplest and most natural of components are required—namely, a resilient meshwork made from proteins and polysaccharides assembled into a multi-scale, hierarchical structure.

At the same time, the finding offers a completely new perspective on how biofilms are immune to so many different types of biocides. Even the most sophisticated biochemical strategy will be ineffective if a biocide cannot enter the slime to reach the bacteria. In short, the antimicrobial activity of alcohols and other solvents becomes compromised by the strongly non-wetting behavior at clinically relevant concentrations.

The team expects that their newfound knowledge will help alert researchers to the need to consider this requirement when designing ways to destroy harmful biofilms.

"Their notorious resistance to a broad range of biocide chemistries has remained a mysterious and pressing problem despite two decades of biofilm research," says Aizenberg, a pioneer in the field of biomimicry. "By looking at it as a macroscopic problem, we found an explanation that was just slightly out of view: antimicrobials can be ineffective simply by being a non-wetting liquid that cannot penetrate into the biofilm and access subsurface cells."

Aizenberg and her colleagues speculate that such strong liquid repellence may have evolved in response to the bacteria's natural soil environment where water can leach heavy metals and other toxins.

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A Bacillus subtilis biofilm, the light-colored, slimy, bacterial coating on top, displays unprecedented liquid repellency as it beads up a drop of ethanol solution that has been placed on it. This remarkable ability offers both a completely new perspective on how biofilms can protect themselves from a wide range of biocides and introduces the first model natural system for broadly non-wetting materials. Credit: Courtesy of the laboratory of Joanna Aizenberg, Harvard School of Engineering and Applied Sciences.

Moreover, the property may underlie the recent success of the use of biofilm as an eco-friendly form of biocontrol for agriculture, protecting plant roots from water-borne pathogens.

Looking ahead, the Harvard team plans to investigate precisely how the biochemical components of biofilms give rise to their exceptional resistance and to test the properties of other bacterial species.

"The applications are exciting, but we are equally thrilled that our findings have revealed a previously undocumented phenomenon about biofilms," says Aizenberg. "The research should be an inspiring reminder that we have only scratched the surface of how things really work."

Just as with biofilm, she adds, "It has been a challenge to get deep into the core of the problem."

Discovering how microbes cooperate

Discovering how microbes cooperate

Ever wonder what microorganisms do on a Saturday night? In professor Derek Lovley's lab at the University of Massachusetts, Amherst, doctoral candidate Zarath Summers and her colleagues made a point to find out. In the process, Summers discovered a new cooperative behavior in bacteria.

"Interspecies electron transfer" entails one microorganism forming a direct electrical connection to another.

Scientists have known since the 1960s that microorganisms can indirectly exchange electrons through a process called hydrogen transfer, in which one microbe produces hydrogen and then another microbe consumes it. But this discovery takes hydrogen transfer and goes a step further. Rather than a baton pass of sorts, it is two species directly plugging into each other.

The microbes Summers and her colleagues are studying - Geobacter - are of particular interest because of their role in environmental restoration. For example, the organisms can destroy petroleum contaminants and remove radioactive metal from polluted groundwater.

Summers recently talked with the Los Angeles Times about her lab work:

Question: What were you originally testing in the lab?

Answer: In the natural environment, there are all sorts of species everywhere, so we wanted to get a handle on what microbes are doing with their friends in the dirt.

We know that the microorganisms living in soil and water are essential for a healthy environment, but we have very little information on how different microbes live together. We wanted to learn more about how they cooperate. What we discovered is that different types of microbes can make electrical connections and pass electricity from one microbe to the other. This allows them to share energy in a highly efficient way that no one has ever seen before.

Q: You essentially placed the microbes in conditions that forced them to work together to survive, using alcohol as an energy source. What is their process?

A: We took two different microbes - Geobacter sulfurreducens and Geobacter metallireducens. They are different species, and only one of them - G. metallireducens - can consume ethanol for energy. They grow in clumps. So the second microbe attaches to the first and, rather than transfer substrates between each other, they are "wired" together and transfer electrons directly. In order to live, the G. sulfurreducens are sucking electrons off of the G. metallireducens.

We essentially put them in a position where they either adapt to work together or they both die. How they are working together has never been seen before in microbiology.

Q: What do they look like?

A: In order to grow and transfer energy, they have to be in these huge clumps together. They are the size of Nerds candy and they're pink, so they look like strawberry Nerds. The clumps are a millimeter or two, which is surprisingly large. You no longer need a microscope to see them. It's microbiology that turned into macrobiology.

Q: You've called these two "the ultimate drinking buddies." Why?

A: Because they have to work together or there's no ethanol consumed.

Q: What are the implications for renewable energy sources?

A: This is a new way to look at how microbe species can live together. Until now people have assumed that when microbes are working together they are transferring substrates between them. What we're saying is direct transfer through "wired" connections is also a possibility. This way of transfer is a much more streamlined way to transfer electrons between microbes. It's like taking an extension cord and plugging it into a neighbor.

Say you want to make a better wastewater treatment reactor. With this new information in hand, now we can possibly help to optimize these systems for faster waste degradation, and more effectively produce valuable biofuels from that waste, thanks to our microbe friends.

Q: What will you test next?

A: There are lots of cases all over the world where there are naturally occurring communities of bacteria that are in close contact, where multiple microbial species are touching - the touching is key for this type of electron transfer. For example, in microbial mats that are as thick as a doormat, or thicker, which grow in temperate climates along coastal regions (such as along the coasts of L.A., San Diego and Mexico), this type of transfer could also be happening.

With the mats, every millimeter you go down within it, there is something different going on - one of the microbes might consume something else that another does not like. There is probably some direct electron transfer going on there.

In wastewater treatment plants, we can take what we know and test different reactors processing all types of waste around the world, to see if there is a direct form of electron transfer happening.