Study Reveals Mechanism of How Cholera Bacteria Communicate

by VR Sreeraman on Nov 15 2007 7:16 PM

Scientists at Princeton University have uncovered a key mechanism in how bacteria communicate with each other, a discovery that could lead to an entirely new class of antibiotics for cholera and other bacterial diseases.

The mechanism has been pinpointed to be CAI-1, a chemical that cholera bacteria use for transmitting messages to each other. Bacteria communicate their presence by emitting chemical messages that their kin recognize. When the messages grow strong enough, the bacteria respond en masse, forming a colony that scientists call a biofilm.

While some colonies of bacteria are fairly harmless, others like that of cholera are less benign. Cholera bacteria use the human intestines as a breeding ground, and after a sizeable colony has formed, they seek to escape the host in order to find other creatures to infect. The bacteria escape by irritating the body, which attempts them out with vomiting and diarrhoea.

However, so violent can be the effect of this that if the body is not quickly rehydrated, a victim can die within a day. Molecular biologist Bonnie Bassler's team realized that the cholera must be signalling each other with some hitherto unknown chemical when the time was right to stop reproducing and exit the body.

This chemical - CAI-1 – which occurs naturally in cholera, was isolated by Dough Higgins, a graduate student in Bassler's lab and first author of the research team's paper on the findings. He then used it to control cholera's behavior in lab tests.

Higgins and the other scientists on the team found that when CAI-1 is absent, cholera bacteria act as pathogens. But when the bacteria detect enough of this chemical, they stop making biofilms and releasing toxins, perceiving that it is time to leave the body instead.

The boffins have also shown that CAI-1 can be used to disrupt the communication that exists among the bacteria, potentially halting the disease's progress. "Disease-causing bacteria talk to each other with a chemical vocabulary, and now we can interfere with their talk to control infections," Nature quoted Higgins, as saying.

"Our findings demonstrate that if you supply CAI-1 to cholera, you can flip their switches to stop the attack. "This paper specifically concerns cholera, but it provides proof in principle that we can do it with any bacteria."

The researchers are now hopeful that it can be applied to other bugs like staph, strep and E. coli that use the same general type of signaling mechanism as cholera.

The paper appears in the online edition of the scientific journal Nature.