The Social Life of Bacteria

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Science  02 Jun 2006:
Vol. 312, Issue 5778, pp. 1279
DOI: 10.1126/science.312.5778.1279c

We know relatively little about the population biology of bacteria in natural environments such as the soil; it is unclear, in particular, whether strains compete or whether the diversity observed is functional. Vos and Velicer investigated genetic diversity in Myxococcus xanthus, a remarkable social bacterium that indulges in swarming, social predation, and, in the face of starvation, can differentiate to form multi-cellular fruiting bodies. Multilocus sequence typing was used to study the evolutionary relationships among isolates sampled from a 16-x-16-cm patch of soil. More than 20 unique genotypes were found that appeared to have evolved clonally. Most were closely related, but there were rare divergent strains that had perhaps blown in as spores. This type of population structure does not resemble the epidemic populations of pathogens, nor does it resemble the emerging picture for marine bacteria, which seem to accumulate neutral mutations that are not regularly purged. Perhaps the spatially structured soil habitat offers clones protection from selective sweeps, or sympatric genotypes may come into contact when swarming or if the soil is disturbed. In the lab, clone pairs of Myxococcus are known to be highly antagonistic; it will be interesting to see how more closely related strains interact under natural conditions. — CA

Appl. Environ. Microbiol. 72, 3615 (2006).

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