May 17, 2006

Bacteria Talking

Are single-celled organisms islands unto themselves? Apparently not. An article in the April 21, 2006 issue of Cell, "Bacterially Speaking" by Bassler & Losick, reviews a growing body of literature exploring bacterial chemical communication, which now appears to be very common.

One widespread means of inter-bacterial communication is called quorum sensing. Each bacteria among the types that use this method puts out a chemical signal whose overall concentration in the environment gives its fellows an idea of how many are present. Such mechanisms cause certain aquatic, bioluminescent bacteria to glow at high concentrations, but not when dispersed. Some species may release chemicals that even interfere with quorum sensing in other bacteria, perhaps allowing them to predominate when competing to infect another organism.

Intercellular communication allows groups of bacteria to develop spore structures that see their genes through harsh times, kill each other off, modulate the gene expression of other bacteria and coordinate streaming movements. The chemicals they produce also contribute to their ongoing competition with fungi and viruses, retarding their growth or even killing them. Some even exude extracellular films of proteins and polysaccharides that hold them together in loose colonies on dry surfaces, a format that reminds me of human connective tissue.

On that note, and by way of purely idle speculation on my part, this seems like exactly the sort of thing you could point out to throw a wrench in the argument of your local anti-evolutionist. They would bring up the ridiculous irreducible complexity doctrine, which states that complex systems serve no function in their smaller or separate parts and thus could not have gradually evolved. Then you could point out that intercellular signaling, for example, predates the development of multicellular organisms like us who rely on it for nerve signaling and hormone regulation.

Posted by natasha at May 17, 2006 10:04 PM | Science | Technorati links |
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