A vascular surgical technique pioneered at UT Southwestern Medical Center and designed to replace infected aortic grafts with the body’s own veins has proved more durable and less prone to new infection than similar procedures using synthetic and cadaver grafts.

Aortic graft infections are one of the most serious complications in patients undergoing aortic grafting procedures for peripheral arterial disease (PAD) and aortic aneurysms. PAD reduces blood circulation in the pelvis and lower extremities, and aortic aneurysms result in a weakening of the aortic wall that can cause lethal rupture of the aorta, the largest artery in the body. Patients with PAD and aortic aneurysms often require surgery, and aortic grafting procedures using synthetic grafts are typically the first line of treatment.

For patients with PAD, the procedure restores blood circulation to the legs, and for patients with aneurysm, it replaces the weakened aortic wall and prevents rupture. Synthetic grafts made of Dacron, a polyester material, are placed in the aorta and femoral arteries in the abdomen and groin, which feed blood to the legs. But in about 1 percent to 2 percent of these patients, the grafts become infected a complication that causes amputation and death if left untreated.

Dr. G. Patrick Clagett, chief of vascular surgery at UT Southwestern, pioneered a technique called the neo-aortoiliac system (NAIS) that repairs these aortic-graft infections. The procedure involves removing the infected graft and replacing it with sections of femoral-popliteal veins harvested from the patient’s thighs, rather than another synthetic graft or vessels harvested from human cadavers.

In a recent study published in the Journal of Vascular Surgery, Dr. Clagett and his team reported on 187 patients at UT Southwestern treated for aortic graft infections who underwent the NAIS procedure from 1990 to 2006. It is the largest group of such patients ever studied, and the researchers found that the incidence of re-infection was lower and the procedure resulted in superior durability with much lower long-term amputation rates when compared with other operations to treat this condition.

“This operation has gained favor worldwide in the treatment of this devastating condition,” said Dr. Clagett. “Since performing the first operation here in the 1990s, we have accumulated data over the years and have found this procedure to be far superior in overall patient outcomes.”

Simply replacing the old Dacron graft with a new synthetic graft can result in devastating infection of the new one, said Dr. Clagett, who is immediate past president of the Society for Vascular Surgery. His team and others also have found that the new synthetic or cadaver grafts tend to develop clots and new blockages.

“When we use the patient’s own tissue to construct a new graft, it provides an advantage because they are less likely to form clots within the graft and less likely to develop new blockages,” Dr. Clagett said. “Patients also need fewer subsequent procedures, a common problem with the other treatments for this complication.”

He added that patients who have the NAIS procedure don’t need to be on lifelong antibiotic therapy. Because the aortic reconstruction is fashioned with the patient’s own tissue, there is no foreign material that is prone to re-infection.

Brazilian researchers have performed the first-ever autopsy study to examine the precise causes of death in victims of the H1N1 swine flu.

“The lack of information on the pathophysiology of this novel disease is a limitation that prevents better clinical management and hinders the development of a therapeutic strategy,” said lead author, Thais Mauad, M.D., Ph.D., associate professor of the Department of Pathology at São Paulo University, in Brazil.

The results of their study will be published in the January 1 issue of the American Thoracic Society’s American Journal of Respiratory and Critical Care Medicine.

The researchers examined 21 patients who had died in São Paulo with confirmed H1N1 infection in July and August, 2009. Most were between the ages of 30 and 59. They found that three-quarters (76 percent) of the patients had underlying medical conditions such as heart disease or cancer, but there was no clear complicating medical condition in the remaining quarter. All presented a progressive and rapidly fatal form of the disease.

While previous data has shown that most patients with a non-fatal infection have fever, cough and achiness (myalgia), Dr. Mauad noted that “most patients with a fatal form of the disease presented with difficulty breathing (dyspnea), with fever and myalgia being less frequently present.”

All patients died of severe acute lung injury, but there were three distinct patterns of the damage to their lungs, indicating that the infection killed in distinct ways. “All patients have a picture of acute lung injury,” said Dr. Mauad. “In some patients this is the predominant pattern; in others, acute lung injury is associated with necrotizing bronchiolitis (NB); and in others there is a hemorrhagic pattern.”

“Patients with NB are more likely to have a bacterial co-infection. Patients with heart disease and cancer are more likely to have a hemorrhagic condition in their lungs. It is important to bear in mind that patients with underlying medical conditions must be adequately monitored, since they are at greater risk of developing a severe H1N1 infection,” said Dr. Mauad. In these patients, H1N1 infection may present as a potential fatal disease, requiring early and prompt intensive care management, including protective ventilation strategies and adequate hemodynamic management. “We found that 38 percent of these patients had a bacterial infection (bronchopneumonia). This has important consequences because these patients need to receive antibiotic therapy, in addition to antiviral therapy.”

Using disinfectants could help superbug bacteria become resistant not only to the disinfectant itself but to antibiotics, even if they have not been exposed to them, according to a new study from Ireland: the findings could be important step in the fight to prevent superbugs spreading in hospitals.

The study is the work of lead author Dr Gerard Fleming from the National University of Ireland (NUI) in Galway, and colleagues, and is available to read online in the January issue of Microbiology. Fleming heads NUI’s Marine Microbiology Laboratory, where as well as researching deep ocean microbes, he and his team investigate cross-resistance between biocide and antibiotics in human pathogens, and assess agricultural workers’ exposure to health hazards.

One of the human pathogens Fleming and his team have been investigating is Pseudomonas aeruginosa, an opportunistic bacterium that can cause infections in people with weak immune systems, cystic fibrosis (CF), diabetes and other diseases. It is an important cause of hospital-acquired infections.

There are two ways of managing hospital-acquired infections: prevention by disinfection of surfaces in the hospital, and treatment by antibiotics: what is worrying about this study is that the bacterium appears to have developed a way to foil both these routes.

Fleming and colleagues reported how by adding more and more disinfectact to lab cultures of P. aeruginosa, they found it adapted to survive not only the disinfectant itself, but also the commonly prescribed antibiotic ciprofloxacin, even without being exposed to it.

The disinfectant they used was benzalkonium chloride (BKC), a bactericide, algaecide and fungicide contained in many hospital, livestock and personal hygiene products, from surface disinfectants to skin sanitizers and cosmetics.

Fleming and colleagues found that the adapted P. aeruginosa had a DNA mutation that allowed it specifically to resist antibiotics like ciprofloxacin and that the mutated bacterial cells had become efficient at pumping out disinfectant and antibiotic agents.

Also important, is they found that adding only very small non-lethal amounts of disinfectant to the culture, made the adapted bacteria more likely to survive than the non-adapted bacteria, which Fleming said establishes the principle that:

“Residue from incorrectly diluted disinfectants left on hospital surfaces could promote the growth of antibiotic-resistant bacteria.”

However, Fleming said they were more worried about the fact that:

“Bacteria seem to be able to adapt to resist antibiotics without even being exposed to them.”

He said it was also important to look at the the environmental factors that might promote antibiotic resistance:

“We need to investigate the effects of using more than one type of disinfectant on promoting antibiotic-resistant strains. This will increase the effectiveness of both our first and second lines of defence against hospital-acquired infections,” said Fleming.

US health officials have confirmed samples from a pair of African drums used in a drumming circle attended by a New Hampshire woman who is severely ill in hospital with gastrointestinal anthrax have tested positive for the deadly bacterium.

The New Hampshire Department of Health and Human Services (DHHS) confirmed on Monday that test samples from two African drums stored at a building belonging to the the United Campus Ministry to the University of New Hampshire in downtown Durham have come back positive for anthrax, but stressed they have not been confirmed as the source of the infection and additional tests are still going on.

The DHHS said that over the weekend, members of the the New Hampshire National Guard, the New Hampshire Department of Environmental Services, and the US Environmental Protection Agency collected environmental samples from the United Campus Ministry building and African drums stored there: the infected woman, who is from Strafford County, took part in a drumming circle held in that building.

The samples are being tested at the New Hampshire Public Health Labs in Concord.

The United Campus Ministry is an ecumenical ministry formed of various denominational Christian bodies that provides spiritual leadership and services on college and university campuses across the US and beyond.

The authorities said they are continuing to investigate the source of the anthrax that infected the woman, and that the drums are only one possible source. In the meantime the building has been closed under an order from DHHS Commissioner Nicholas Toumpas until further notice.

In an earlier media communication on Sunday Toumpas said:

“Our thoughts and concerns are with this patient and her family.”

“This is a difficult and unusual situation, and we are committing all possible resources to determining the cause of this exposure as quickly as possible.”

Public Health Director Dr. José Montero told the media that:

“Gastrointestinal anthrax is very unusual.”

“We have not yet been able to confirm that the drums are the cause of the patient’s illness and we are continuing to follow up many leads. Anthrax is not an illness that you can catch from someone else.”

Anthrax is an acute infectious disease caused by the spore-forming bacterium Bacillus anthracis.

It is rare for humans to become infected with anthrax, as it most commonly occurs in wild and domestic animals such as cattle, sheep, goats, camels, antelopes, and other plant-eaters. Anthrax occurs naturally all over the world, but is more common in countries without veterinary public health programs.

Humans can’t catch anthrax from an infected human: they catch it from being exposed to infected live animals or dead tissue from animals, including hides, meat, and fur (African drums are usually made from hollowed out logs and stretched cow skin).

Although it is very rare for people to become infected naturally by anthrax, public concern has been heightened in recent years because the bacterium has been been weaponized, as in October 2001, when mail containing spores of the bacterium was sent to US senator Tom Daschle, media offices, and others, killing five people and infecting 17 more. There are also concerns about its wider potential use in biological warfare.

There are three types of anthrax infection: cutaneous (skin), inhalation, and gastrointestinal. Symptoms vary depending on how it is contracted, but they usual appear within 7 days.

The intestinal form, which is what the woman at the centre of this case has been diagnosed with, starts with nausea, loss of appetite, vomiting, and fever, followed by abdominal pain, vomiting of blood and severe diarrhea.

Mortality rates vary from 20 per cent of untreated skin cases, around 50 per cent for the gastrointestinal form, to fatal if it is breathed in.

The New Hampshire DHHS said that even though it is a remote possibility for transmission, because of the possible link to the African drums, they are asking:

“Anyone who brought their own drum to one of the events held at the United Campus Ministry between October 1st and early December 2009 to call DPHS at 271-4496 to discuss the possibility of having their drum tested.”

An estimated 25,000 Americans develop severe fungal infections each year, leading to 10,000 deaths despite the use of anti-fungal drugs. The associated cost to the U.S. health care system has been estimated at $1 billion a year.

Now two Syracuse University scientists have developed new brominated furanones that exhibit powerful anti-fungal properties.

The most virulent fungus is Candida albicans, which is carried by about 75 percent of the public. Typically the fungus is harmless but, in individuals with HIV or otherwise compromised immune systems, it can cause candidiasis, which has a high mortality rate. The fungi can also form biofilms that attach to surfaces and are up to 1,000 times more resistant to anti-fungals.

“These new furanones have the potential to control such infections and save lives,” says assistant professor Dacheng Ren of the Department of Biomedical and Chemical Engineering in SU’s L.C. Smith College of Engineering and Computer Science. “In our tests, they reduced fungal growth by more than 80 percent, and we hope to improve on that going forward.”
Over the past 20 years, pathogenic fungi have developed growing resistance to anti-fungal drugs. This stimulated a strong demand for more effective drugs and led to the successful research at Syracuse. The researchers’ genomic study suggests that furanones have different genetic targets than current anti-fungal agents and thus may avoid drug resistance acquired in the past. The research team has also shown previously that these furanones inhibit bacterial biofilm formation; thus they may help control chronic infections where biofilms often appear, on surgical, dental and other implants.

A team of researchers working in a high containment laboratory at the Centers for Disease Control and Prevention in Atlanta, GA, have solved a fundamental mystery about smallpox that has puzzled scientists long after the natural disease was eradicated by vaccination.: they know how it kills us. In a new research report appearing online in The FASEB Journal, researchers describe how the virus cripples immune systems by attacking molecules made by our bodies to block viral replication. This discovery fills a major gap in the scientific understanding of pox diseases and lays the foundation for the development of antiviral treatments, should smallpox or related viruses re-emerge through accident, viral evolution, or terrorist action.

“These studies demonstrate the production of an interferon binding protein by variola virus and monkeypox virus, and point at this viral anti-interferon protein as a target to develop new therapeutics and protect people from smallpox and related viruses,” said Antonio Alcami, Ph.D., a collaborator on the study from Madrid, Spain. “A better understanding of how variola virus, one of the most virulent viruses known to humans, evades host defenses will help up to understand the molecular mechanisms that cause disease in other viral infections.”

In a high containment laboratory at the Centers for Disease Control and Prevention in Atlanta, scientists produced the recombinant proteins from the variola virus and a similar virus that affects monkeys, causing monkeypox. The researchers then showed that cells infected with variola and monkeypox produced a protein that blocks a wide range of human interferons, which are molecules produced by our immune systems meant to stop viral replication.

“The re-emergence of pox viruses has potentially devastating consequences for people worldwide, as increasing numbers of people lack immunity to smallpox,” said Gerald Weissmann, M.D., Editor-in-Chief of The FASEB Journal. “Understanding exactly how pox viruses disrupt our immune systems can help us develop defenses against natural and terror-borne pox viruses.”

Researchers at Binghamton University, State University of New York, have identified three key regulators required for the formation and development of biofilms. The discovery could lead to new ways of treating chronic infections.

Biofilms communities of bacteria in self-produced slime may be found almost anywhere that solids and liquids meet, whether in nature, in hospitals or in industrial settings. Biofilms are implicated in more than 80 percent of chronic inflammatory and infectious diseases caused by bacteria, including ear infections, gastrointestinal ulcers, urinary tract infections and pulmonary infections in cystic fibrosis patients, according to the Centers for Disease Control.

Biofilms are difficult to eradicate with conventional antimicrobial treatments since they can be nearly 1,500-fold more resistant to antibiotics than planktonic, free-floating cells. Biofilms also pose a persistent problem in many industrial processes, including drinking water distribution networks and manufacturing.

Karin Sauer, associate professor of biology at Binghamton University, and graduate student Olga Petrova published their findings of key regulatory events required for the formation and development of Pseudomonas aeruginosa biofilms in PLoS Pathogens, a peer-reviewed, open-access journal published online by the Public Library of Science.

“We have found a pathway of how the formation of biofilms is controlled,” Sauer said. “If we can figure out how to make use of this newly discovered genetic program, we can interfere with the formation of biofilms and either prevent or treat biofilm infections more successfully.”

Pseudomonas aeruginosa, an opportunistic pathogenic bacterium, is considered one of the primary causes of death in patients with cystic fibrosis, a common and life-threatening hereditary disease.

Petrova documented a previously unknown genetic program composed of several regulators by looking for changes in phosphorylation patterns in Pseudomonas aeruginosa. These regulators cannot only be used to stop the development of biofilms at various stages in their growth but also to revert established biofilms to an earlier developmental stage.

“The problem you have when you have a chronic infection is that your immune system is trying to clear the infection but is unable to,” Sauer said. “And the longer the chronic infection goes on, the more damage there will be to tissue at the site of the infection. That’s because the immune response often involves the release of toxic compounds that have no effect on biofilms but can damage the surrounding tissues.”

Sauer’s research is driven by several key questions, she said: “Can we outsmart the biofilms? Can we interfere with biofilm antibiotic resistance? Can we figure out how to prevent biofilms from forming and becoming resistant to antibiotics?”

Some recent findings seem to offer a resounding yes to these questions. In addition to regulators required for biofilm formation, Sauer and her team recently identified a regulator that is only expressed in biofilms and which seems to be responsible for regulating antibiotic resistance.

“We can modulate the resistance of biofilms now by over-expressing or inactivating this particular regulator,” she said. “We hope to use these discoveries to treat infections by interfering with the way biofilms are growing and by reverting biofilms back to a state where they’re more easily treatable.”

Sauer’s research is supported by the National Institutes of Health, which has awarded her more than $3 million, and the Army Research Office. Her two major NIH-funded projects, which began this fall, look at different aspects of biofilms. One focuses on antibiotic resistance and the mechanism behind it; the other centers on dispersion, the process by which a biofilm breaks down into individual bacterial cells.

“Dispersed cells or planktonic cells are way easier to treat,” Sauer said. “We want to understand how bacteria decide when to leave the biofilm. We can use that as a way to treat chronic infections.”

Scientists studying how bacteria under stress collectively weigh and initiate different survival strategies say they have gained new insights into how humans make strategic decisions that affect their health, wealth and the fate of others in society.

Their study, published in the early online edition of the journal Proceedings of the National Academy of Sciences, was accomplished when the scientists applied the mathematical techniques used in physics to describe the complex interplay of genes and proteins that colonies of bacteria rely upon to initiate different survival strategies during times of environmental stress. Using the mathematical tools of theoretical physics and chemistry to describe complex biological systems is becoming more commonplace in the emerging field of theoretical biological physics.

The authors of the new study are theoretical physicists and chemists at the University of California, San Diego’s Center for Theoretical Biological Physics, the nation’s center for this activity funded by the National Science Foundation, and Tel Aviv University in Israel. They say that how genes are turned on and off in bacteria living under conditions of stress not only shed light on how complex biological systems interact, but provide insights for economists and political scientists applying mathematical models to describe complex human decision making.

“Everyone knows the need to try to postpone important decisions until the last moment but apparently there are simple creatures that do it well and therefore can really teach us – the bacteria,” said Eshel Ben Jacob, a physics professor at Tel Aviv University and a fellow of the Center for Theoretical Biological Physics. He co-authored the study with three other scientists at the center: José Onuchic, a professor of physics at UCSD and a co-director of the center, Peter Wolynes, a professor of physics and chemistry at UCSD and Daniel Schultz, a postdoctoral researcher at UCSD.

In nature, bacteria live in large colonies whose numbers may reach up to 100 times the number of people on earth. Many bacteria respond to extreme stress – such as starvation, poisoning and irradiation – by creating spores, dormant states that are highly resistant to the outside environment and that can germinate into fully functioning bacteria once the environment improves. The response involves more than 500 genes and takes about 10 hours in Bacillus subtilis, the bacterium used by the scientists in their study.

Each bacterium in the colony communicates via chemical messages and performs a sophisticated decision making process using a specialized network of genes and proteins. Modeling this complex interplay of genes and proteins by the bacteria enabled the scientists to assess the pros and cons of different choices in game theory, a branch of mathematics that attempts to model decision making by humans, in which an individual’s success in making choices depends on the choices of others.

When bacteria form spores, the mother cell dies, but not before it stores a copy of its DNA in a special capsule called the spore. The mother cell then breaks open and its DNA and remaining proteins are released to the environment. The bacteria on the road to spore formation don’t always form spores. They can change their fate and escape into a different state called “competence.”

In this state, the bacteria change their membranes to allow the easy absorption of material from the dying cells. This allows for the creation of a “competence intermediate state,” in which the bacteria hope to survive even under these unfriendly conditions. When normal conditions are restored, bacteria return to normal life without having to make a spore. The advantage of this situation is the ability of quickly returning to normality, but there is also a disadvantage: Likely death if the conditions get even worse. As a result, each bacterium has a dilemma.

“It pays for the individual cell to take the risk and escape into competence only if it notices that the majority of the cells decide to sporulate,” explained Onuchic. “But if this is the case, it should not take this chance because most of the other cells might reach the same conclusion and escape from sporulation. Observations have shown that indeed only about 10 percent of the bacteria enter into competence. But how they make this decision and which cells take this chance have been a mystery.”

The researchers discovered in their study that the bacteria’s game theory decision making process is far more advanced than the well-known game theory problem known as the Prisoner’s Dilemma.

Classic Prisoner’s Dilemma, when applied to two prisoners, gives them the following offer: If only one prisoner pleads guilty, the one that cooperates gets two years in jail while the other one gets six years. If both of them admit guilt, then they will be imprisoned for four years. However, if none of them pleads guilty, they go free with no punishment. The temptation is not to admit anything, but the prisoners never know whether or not the other prisoner cooperated and pled guilty.

Because the number of participants in a bacterial colony can be up to 100 times the number of people on earth, the bacteria need to construct a more complex form of game theory. The rapidly changing environmental conditions they face means also bacteria have limited time to decide.

“Prisoner’s Dilemma for bacteria is more complex,” said Ben Jacob. “Each bacterium must decide whether to become a spore; that is, to cooperate, or escape into competence, or take advantage of the others, while it has a limited time to decide while a clock is ticking. We discovered that each cell has an internal timer whose pace changes according to the stress it experiences – the pace goes up for higher stress decisions such as in humans. Our internal clock speeds up under danger because of the secretion of adrenaline and therefore we have the sensation of time slowing down. In addition to internal stress, each bacterium adjusts the pace of its timer accordingly to the stress of its peers and their intention to sporulate or to go into competence.”

According to Onuchic, bacteria usually do not cheat their friends and inform them by sending chemical messages about their true intensions.

“We have developed for the first time a system level model of a large gene network to decipher the underlying principles of the bacteria game theory and how an internal network of genes and proteins is used to calculate risks in this complicated situation,” he said.

This has applications to human society because many people encounter similar dilemmas during their own lives. For example, should people ignore side effects and vaccinate against a new potentially lethal virus or should they not vaccinate and take the risk of being infected with the possible consequences? If the majority of the population is going to get vaccinated, then it is better for each individual not to get vaccinated. However, if most people will not be vaccinated then it is better to be vaccinated.

“What each bacterium is doing is the equivalent if each individual on earth was able receive the exact information about the rate of spread of this new virus, the exact information about the intensions, to be vaccinated or not, by each person on the planet, and in addition the exact information about the health risks of side effects or being infected,” said Ben Jacob. “A decision is then made in the context of this vast amount of information.”

“We have shown how the bacteria do this complex calculation according to well-defined principles,” added Onuchic. “We learned a simple rule: Anyone who needs to make a decision under pressure in life, especially if it is a possible death decision, will take its time. She or he will review the trends of change, will render all possible chances and risks, and only then react.”

“Another interesting fact is that the same cells in the same environment, in this case, bacteria in the colony, can actually in a statistical matter choose two different outcomes: sporulation or competence. This leads us to speculate whether similar ideas can be extrapolated to explain the decisions of cells to develop cancer: Can a similar cell in a tissue make the decision to duplicate normally or to modify into a cancer cell? How does this stochastic process affect life, biology, evolution and disease is an interesting challenge that will be at the center of questions answered at the interface of the physical and life sciences.”

MIT and Boston University researchers have discovered that the drug hydroxyurea kills bacteria by inducing them to produce molecules toxic to themselves -a conclusion that raises the possibility of finding new antibiotics that use similar mechanisms.

Hydroxyurea inhibits the enzyme critical for making the building blocks for DNA, so for decades it has been used to study the consequences of inhibiting DNA replication in E. coli, yeast and mammalian cells. It is also sometimes used in chemotherapy to halt the growth of cancer cells.

The research team, led by biologist Graham Walker of MIT and bioengineer James Collins of Boston University, showed that cells don’t die after hydroxyurea treatment because their DNA replication is blocked, but because the blockage sets in motion a chain of cellular events that culminates in the production of hydroxyl radicals. Those radicals are highly reactive and can damage cellular molecules such as nucleic acids, lipids and proteins.

Collins has previously shown that three different antibiotics, which each inhibit different cell processes, all lead to production of hydroxyl radicals, which play a role in killing the cells.

“This naturally leads to the thought that one could perhaps find a new class of antibiotic that acts further down the chain(s) of events that stimulate hydroxyl radical production,” says Walker.

The findings could also aid in the development of adjuvants – small molecules that would enhance the lethality of current antibiotics, says Collins.

How they did it: The researchers exposed E. coli to hydroxyurea, provoking them to activate a DNA repair system called SOS. This response keeps the cells alive for several hours, but eventually produces hydroxyl radicals that kill the bacteria.

Next steps: In future studies, Walker hopes to delve further into the mechanism of bacterial response to hydroxyrurea and the sequence of events that ultimately kills them.

Proteins, which perform such vital roles in our bodies as building and maintaining tissues and regulating cellular processes, are a finicky lot. In order to work properly, they must be folded just so, yet many proteins readily collapse into useless tangles when exposed to temperatures just a few degrees above normal body temperature.

This precarious stability leaves proteins and the living beings that depend upon them on the edge of a precipice, where a single destabilizing change in a key protein can lead to disease or death. It also greatly complicates the manufacture and use of proteins in research and medicine.

Finding a way to stabilize proteins could help prevent such dire consequences, reduce the very high cost of protein drugs and perhaps also help scientists understand why proteins are often so unstable in the first place. In a paper published in the Dec. 11 issue of the journal Molecular Cell, researchers at the University of Michigan and the University of Leeds describe a new strategy for stabilizing specific proteins by directly linking their stability to the antibiotic resistance of bacteria.

“The method we developed should provide an easy way to strengthen many proteins and by doing so increase their practical utility,” said James Bardwell, a Howard Hughes Medical Institute investigator and professor of molecular, cellular and developmental biology at U-M.

In the new approach, the researchers found that when a protein is inserted into the middle of an antibiotic resistance marker, bacterial antibiotic resistance becomes dependent upon how stable the inserted protein is. This enabled the scientists to easily select for stabilizing mutations in proteins by using a simple life-or-death test for bacterial growth on antibiotics. The mutations the scientists identified rendered proteins more resistant to unfolding.

“This method also has allowed us to catch a glimpse of why proteins may need to be just barely stable,” said Linda Foit, the graduate student at U-M who initiated the work. “The mutations that we found to enhance the stability of our model protein are mostly in key areas related to the protein’s function, suggesting that this protein may need to be flexible and therefore marginally stable in order to work. It may be that, over the course of evolution, natural selection acts to optimize, rather than maximize protein stability.”