Variety—the Splice of Life—in Microbial Communities

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Science  27 Nov 2009:
Vol. 326, Issue 5957, pp. 1198-1199
DOI: 10.1126/science.1181501

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Bacteria and Archaea are commonly thought to exist as clonal populations because they reproduce asexually. However, genomic studies have shown that the evolutionary trajectories of most bacterial and archaeal populations are profoundly modified by exchange of genetic information, which creates natural populations that are inherently diverse. Much of this genomic variation confers no selective advantage or leads to evolutionary dead ends, some provides the raw material for selection that gives rise to new capabilities and lineages, and some may be critically involved in defense against mobile elements. Recently, it has become apparent that many Bacteria and Archaea splice into their genomes tiny fragments from the viruses and other mobile elements that harness them to replicate and survive. The uptake of these fragments can be so rapid that most bacterial and archaeal cells in a single population could be genomically distinct at the hypervariable locus where fragment insertion occurs. Variety that results from this diversification process could, in some cases, be critical to host population survival.