Obviously bacteria are single celled organisms and don't speak or see or hear as we do. But, sometimes they only carry out certain activities when there are large numbers of their species present. For example, some bacteria will only launch a virulent attack if there's a large group of them so that they will have a better chance at success.
So, these researchers have tried to understand how it is that bacteria "know" that there are other bacteria like them around.
The first place they looked was at an organism called Vibrio fischeri, which makes light: it has bioluminescence. When they are alone, no light is produced, but when there is a particular number of them close together, they light simultaneously. They have a symbiotic relationship with a squid which keeps them on board as a camouflage from predators at night, then in daylight, pumps 95% of them out, and they stop producing light. Those left with the squid grow and divide during the day and by the time night comes again, they have reached a certain population and all light up again.
The commonality is in a simple molecule produced by the bacteria. Each bacteria within a species produces it, and also has an exterior receptor, which fits the molecule in a lock and key fashion. The mechanism allows the bacteria to register whether there is a large concentration of the molecule around it, and therefore whether there are enough of the same species around to do whatever collective job they need to do. If there is, the mechanism will go and switch on all the genes needed to do that work, to perform those collectivebehaviours.
Thus the phrase "quorum sensing": bacteria can check out whether there's enough of them around to get something done.
The researchers have found that this mechanism is common for most if not all bacteria, and that there are receptors and molecules not only for inter-species communication, but intra-species as well. So bacteria can tell how many of other species of bacteria are around. All bacteria produce and have receptors for the simple 5-carbon molecule pictured.
The exciting thing about this research is that it looks like a possible solution to the problem of antibiotic resistance. If bacteria don't know that each other are around because their eyes and ears are blocked, maybe they won't launch virulent group behaviours. Further testing and studies are being undertaken in this area, by looking at ways of blocking the receptor sites with similar molecules.
References:
Interview with Bonnie Bassler: http://blog.ted.com/2009/04/the_secret_soci.php
Video: http://www.ted.com/index.php/talks/bonnie_bassler_on_how_bacteria_communicate.html
Bonnie Bassler's homepage: http://www.molbio.princeton.edu/index.php?option=content&task=view&id=27
Posted By Peggy Newman
