( the circumstances warrant. Researche...)Say what? Bacterial conversation stoppers

Researchers have speculated that AI-2 is a universal language, and the new study from Bassler's lab is the first to show those conversations taking place ?and producing consequences -- between co-mingling species.

Postdoctoral fellow Karina Xavier mixed E. coli, beneficial bacteria that live in the human gut, with Vibrio harveyi, a marine species that naturally glows in the dark in the presence of a crowd. In the test tube, AI-2 production by either species turned up the marine bacteria's light and turned on the quorum-sensing genes in E. coli. That confirmed what the scientists already suspected: the linguistic versatility of AI-2.

But this common language does not guarantee the correct message gets through, the researchers discovered. In earlier work, Xavier had found that E. coli both produces and consumes AI-2. In this study, she set up an experiment where multitudes of E. coli first produced then devoured enough AI-2 to dim the lights of the marine bacteria, essentially fooling the thriving oceanic gang into thinking its members were few, thereby terminating its quorum-sensing behaviors.

In a more realistic encounter, Xavier mixed E. coli with V. cholerae, the cholera-causing bacteria that mixes with E. coli in human guts. When cholera bacteria sense a quorum, they turn off their toxins and excrete an enzyme to cut themselves loose from the intestine, so they can move out of the body where they can infect another person. Here, E. coli squelched much of the quorum-sensing response of the cholera bacteria, although the effect was not as dramatic as with the marine bacteria.

"The real take-home point is the interference," Bassler said. "Consumption of the signal could be a mechanism that allows one kind of bacteria to block another kind of bacteria from counting how many neighbors they have and, in turn, properly controlling its beh
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Source:Howard Hughes Medical Institute