Tuesday, April 15, 2008

Gut bacteria species becoming one

Humans may have helped organisms shack up inside animal intestines. Chicken farms may be, in part, responsible for the rapid merging of two different Campylobacter bacteria species. Like lovers reunited after a cruel world tore them apart, two species of bacteria have found each other in the guts of domestic livestock and are becoming one.

Campylobacter jejuni and Campylobacter coli, as the intestinal organisms are known, aren't just consummating their microscopic love by exchanging genes — they're merging into a single species, scientists say.

The researchers think the marriage of the creatures represents a profound example of how people can affect evolution. "What we're seeing here is hybridization, and it's only been recently acknowledged as an important part of evolution," said Samuel Sheppard, an evolutionary microbiologist at Oxford University in the United Kingdom. "It's really exciting stuff."

Sheppard and his colleagues detail their findings today in an advance online version of the April 11 issue of the journal Science. The team reached their conclusions by analyzing DNA, or genetic information, from the bacteria found inside both wild and farm animals.

Ancient split
C. jejuni and C. coli are thought to have shared a common ancestor, or parent, in the ancient past. When the microbial descendent split up and evolutionary pressures stepped in, two new species began to take shape and fill different niches within the guts of wild chickens, pigs and other animals.

Although the definition of a species is one of the most hotly debated topics among biologists, Sheppard said the two microbes are strikingly different, despite sharing about 85 percent of their genetic code.

"Chimpanzees and humans are known to be about 98 percent genetically similar, so the bacteria's converging toward becoming a single species, as we think, is pretty impressive," Sheppard told LiveScience. "That's a big genetic gulf to leap. Maybe like a lobster mating with a fly."

Sheppard said the bacteria likely began reversing their growing divergence, or genetic separation, when human agriculture came along.

Under pressure
He thinks the bacterial merger has accelerated in recent years, as the world has become more industrialized and the demand for food has prompted crowded farms. - msnbc

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