Welcome to the Microbiology Information

Helmholtz Association of German Research Centres - Science Daily — A German-American research team of biologists and geochemists has discovered hitherto unknown anaerobic bacteria in marine sediments which need only propane or butane for growth, as recently reported by the scientific journal “Nature.”

The hydrocarbons ethane, propane and butane — as well as the main component, methane — are the major constituents of natural gas.

Biological processes may lead to the degradation of these hydrocarbons in underground petroleum reservoirs and other geological habitats.

Heinz Wilkes, a leading biogeochemist at GeoForschungsZentrum Potsdam (GFZ), points out: “The bacteria isolated here for the first time from marine sediments use sulphate instead of oxygen for respiration and utilize propane and butane as their sole source of carbon and energy. These organisms are tough specialists that have become adapted to strictly utilising only these and no other substrates.”

The investigations showed that the bacteria employ an unprecedented biochemical mechanism for transforming what are essentially unreactive hydrocarbons into reactive metabolites which may then be further oxidised to carbon dioxide.

The findings concerning this reaction mechanism are an important step in designing new synthetic methods for selectively producing chemicals from hydrocarbons.

North Carolina Sea Grant researchers have isolated a new peptide antibiotic from the American oyster that may have implications for managing many diseases in oysters.

The new antimicrobial peptide “American oyster defensin” (AOD) may protect against bacteria in Crassostrea virginica, a species that is native to North Carolina and important economically to Atlantic and Gulf Coast fisheries.

“This peptide may be helpful in selecting disease-resistant oysters for aquaculture and fisheries and may also allow for the development of a test to monitor oyster health,” says Ed Noga, professor at the North Carolina State University College of Veterinary Medicine.

“In recent years, a number of pathogens, especially bacteria and parasites, have devastated American oyster populations.”

The research findings appear in the new (Dec. 30) issue of Biochemical and Biophysical Research Communications.

Pathogens such as dermo (Perkinsus marinus) have caused major decreases in oyster productivity — bacterial pathogens — such as Vibrio vulnificus that can cause a food-borne illness are a human health concern, according to Noga.

This is the first time that researchers have isolated an antimicrobial peptide from any oyster species, he says.

NC State veterinary medicine postdoctoral research associate Jung-Kil Seo, as well as scientists J. Myron Crawford and Kathryn L. Stone of Yale University’s Keck Biotechnology Resource Laboratory, collaborated with Noga on the study.

“The results may be used to better understand the innate immune system of American oysters and to enhance research to protect it from important microbial infections,” according to Noga.

“Further studies are needed to identify sites of synthesis and storage of AOD and determine mechanisms affecting its regulation.”

According to New Scientist, “A comprehensive analysis of both the molecular genetic and phenotypic responses of any organism to the space flight environment has never been accomplished because of significant technological and logistical hurdles.”……until now.

Bacteria flown on the space shuttle mutated in ways that made them nearly three times more deadly to mice, reports a new study. While the bugs are also likely to affect astronauts’ health, the research team found clues that may help render them harmless.

Astrobiologists have long been worried that the low-gravity conditions of space could make disease-causing microbes that hitch-hike on shuttle missions mutate in unpredictable ways. To investigate, Cheryl Nickerson at Arizona State University in Tempe, US, and her colleagues launched flasks of the bacterium Salmonella typhimurium into space on the shuttle Atlantis in September 2006.

The shuttle returned after 12 days, during which time the microbes had altered the way they express 167 genes compared with bacteria that remained on Earth. The team found that these space-mutated bugs were almost three times as likely to kill infected mice compared with their ground-grown counterparts.

That could be bad news if the results hold true for astronauts, since some experiments suggest the weightlessness of space travel suppresses the immune system.

But the news is not all bad. Nickerson and her colleagues also identified the protein, called Hfq, believed to be behind the change. “An overwhelming number of the [affected] genes are regulated by Hfq,” she says.

Archilles’ Heel
Strains of Salmonella without normally functioning Hfq did not show the gene expression changes when they were tested under microgravity conditions in the lab. Nickerson says this knowledge could one day be leveraged to “design targeted strategies and countermeasures to mitigate infectious disease risks to the crew during future missions”.

The work may also help combat Salmonella on Earth. Micro-organisms growing in a liquid in microgravity experience low fluid forces that are similar in many ways to those that the bugs encounter on Earth inside their hosts, she explains. “An exciting part of this work is the opportunity to use spaceflight as a novel research platform for innovations in infectious disease control here on Earth,” she told.

Robert McLean, a microbiologist at Texas State University in San Marcos, US, who has also flown bacterial experiments on space shuttles, is impressed with the new study.

“On Earth, we’re so used to gravity that we ignore it, but for the first time we’re seeing that gravity may be needed for genes to be expressed,” he told New Scientist. “I think that transcends the space programme, and tells us something hugely important about biology in general.”

An unexpected find by a team of University of Georgia scientists suggests that reducing the use of antibiotics on poultry farms will do little, if anything to reduce rates of antibiotic resistant bacteria that have the potential to threaten human health.

Dr. Margie Lee, professor in the UGA College of Veterinary Medicine, and her colleagues have found that chickens raised on antibiotic-free farms and even those raised under pristine laboratory conditions have high levels of bacteria that are resistant to common antibiotics. Her findings, published in the March issue of the journal Applied and Environmental Microbiology, suggest that poultry come to the farm harboring resistant bacteria, possibly acquired as they were developing in their eggs.

“The resistances don’t necessarily come from antibiotic use in the birds that we eat,” Lee said, “so banning antibiotic use on the farm isn’t going to help. You have to put in some work before that.”

Lee and her team sampled droppings from more than 140,000 chickens under four different conditions: 1.) commercial flocks that had been given antibiotics; 2.) commercial flocks that had not been given antibiotics; 3.) flocks raised in a lab that had been given antibiotics; and 4.) flocks raised in a lab that had not been given antibiotics. The researchers examined levels of antibiotic resistance in normal intestinal bacteria that do not cause human illness and – in a companion study published in May in the same journal – also examined levels of drug resistant campylobacter bacteria, a common food-borne cause of diarrhea, cramping and abdominal pain.

They found that even chickens raised in the pristine laboratory conditions had levels of antibiotic resistance levels comparable to what was seen on farms that used antibiotics. Even when the levels were lower, Lee adds, they were still well above the reasonable comfort zone for antibiotic resistance – roughly five to 10 percent.

Seventy-three percent of the bacteria from one flock in the antibiotic-free commercial group were resistant to the drug oxytetracycline, for example, while 90 percent were resistant to the drug in a commercial flock that used antibiotics. Ninety-seven percent were resistant in the experimental flock that was given antibiotics, while forty-seven percent were resistant in the experimental group that was not given antibiotics.

Strikingly, they even found bacteria resistant to streptomycin, a common human antibiotic that is rarely used in poultry and was not used on the farms the researchers studied.

Bacteria swap genes relatively easily, and Lee explained that the concern is that drug resistance genes from bacteria that infect poultry could be passed on to bacteria that cause human illness. With these resistance genes, human bacterial illness could become harder to treat.

These concerns led the European Union to ban the use of antibiotics for growth promotion in chickens in 2006. In 2005, the U.S. Food and Drug Administration banned the use of the drug Baytril (the brand name for enrofloxacin, a fluoroquinolone antibiotic) in poultry, citing concerns that it could lead to resistance in human antibiotics such as Ciprofloxacin, also a fluoroquinolone.

Several advocacy groups are pushing for a more comprehensive animal antibiotic ban in the United States, but Lee said her research plus the evidence from the Baytril ban suggests that approach won’t help.

“They banned Baytril in 2005, and if you look at Baytril resistance in campylobacter now it’s essentially unchanged,” Lee said.

In previous studies, Lee has tried to recreate experimentally conditions that should lead to the swapping of resistance genes among bacteria. Lee said these events – known as the horizontal transfer of genes – do occur, but they may not be as common as initially thought.

What may be driving the antibiotic resistance that Lee has observed in her studies is what’s known as vertical transfer – from parent to child – of bacteria carrying resistance genes. In short, the birds may come to the farm harboring antibiotic resistant bacteria.

“This issue of antibiotic resistance is more complicated than once thought,” Lee said. “These findings suggest that banning antibiotics at the farm level may not be as effective as assumed. We need further studies to identify which management practice would be effective”

Lee stresses that for consumers, the advice on poultry is the same that it’s always been. Cook meat thoroughly and use proper food handling and preparation techniques – washing your hands regularly and keeping other foods away from raw chicken, for example – to minimize the risk of illness.

“All foods have the potential to contain pathogens – all of them,” Lee said. “There’s no substitute for good food handling and preparation.”

The study was funded by grants from the FDA and the United States Department of Agriculture.