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A Germ-Eat-Germ World

photo - researcher hold up cholera plate

Eryn Bernardy, a doctoral candidate in Georgia Tech’s School of Biological Sciences, holds an agar plate on which cholera colonies (yellow) are growing. Photo: John Toon

In humans, cholera is among the world’s most deadly diseases. But in aquatic environments far from people, the same bacterium attacks neighboring microbes with a toxic spear — and often steals DNA from other microorganisms to expand its own capabilities.

A study of more than 50 samples of Vibrio cholerae isolated from patients and the environment demonstrates the diversity and resourcefulness of the organism. In the environment, the cholera bacterium is commonly found attached to chitin, a material used by aquatic creatures such as crabs to form protective shells. In the wild, most strains of cholera can degrade the shells for food, and the new study showed how the presence of chitin can signal the bacteria — which have receptors for the compound — to produce behaviors very different from those seen in human disease.

Among the cholera strains studied, less than a quarter were able to take up DNA from other sources. Almost all of the samples taken from the environment were able to kill other bacteria — a phenomenon called “bacterial dueling” — but just 14 percent of the bacterial strains isolated from humans could do so.

“It’s a dog-eat-dog world out there even for bacteria,” said Brian Hammer, an associate professor in the Georgia Tech School of Biological Sciences. “Bacteria such as Vibrio cholerae sense and respond to their surroundings, and they use that information to turn on and off the genes that benefit them in specific environments.”

The research, supported by the National Science Foundation and the Gordon and Betty Moore Foundation, provides information that could lead to development of better therapeutic agents against the disease. The research was conducted with assistance from the Centers for Disease Control and Prevention and was reported in the journal Applied and Environmental Microbiology. — John Toon

photo - Brian Hammer

Brian Hammer is an associate professor in Georgia Tech’s School of Biological Sciences.

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