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Chemical Reaction: Talking Germs

By: Steve Herman
Posted: August 7, 2007, from the August 2007 issue of GCI Magazine.

What Noam Chomsky is to linguistics, Princeton University’s Bonnie Bassler is to bacterial conversations.

Anthropological science has made plain the myriad communication structures utilized by humans, as well as animals—albeit the latter at a less sophisticated level. Would it come as a surprise that bacteria can also communicate? Quorum sensing, one version of bacterial communication, has become an important tool for a deeper understanding of the living world.

Bassler is working to answer questions of bacteria’s importance for cosmetics. The phenomenon called quorum sensing was first found in only a few examples, most notably Vibrio harveyi, but it is now known to be much more extensive.

When a person is infected by harmful bacteria, the body sends a few antibodies to destroy the invaders. As strange as it seems, bacteria know this. No organism could have survived a billion years without some common sense. The bacteria don’t shout, “Here we are!”—they instead ask, “Anybody here?” and lay low. But as more and more bacteria show up, eventually a viable army is assembled and an attack commences. Your body is challenged to handle this invasion and you call in sick.

The questioning (“Anybody here?”) is done by a quorum-sensing molecule. Bacteria are pretty smart little guys, and have developed one language to talk to each other and a different language to talk between species. Bacterial cell communication involves the exchange of chemical signal molecules called autoinducers. Figure 1 shows the V. Harveyi quorum-sensing circuit.