The losers in that manipulation are always the males of the host organism. Depending on the specific pair of Wolbachia and host species involved, the host males are either killed, converted into females, or prevented from successfully fertilizing the eggs of uninfected females.

Scientists have now shed light on the biology and evolution of these amazing bacteria by deciphering and analyzing the genome of a model Wolbachia strain, Wolbachia pipientis wMel, which infects the fruit fly Drosophila melanogaster, itself a model for studies of animal biology.

The new study, which appears in the March 2004 issue of PloS Biology, presents the first complete genome of a Wolbachia species. The project was supported by a grant from the National Institute of Allergy and Infectious Diseases (NIAID), which is part of the U.S. National Institutes of Health.

The investigators, led by Jonathan Eisen of The Institute for Genomic Research (TIGR), found that composition of the genome was very different from that of other intracellular bacteria. The wMel genome has accumulated more repetitive and so-called "junk" DNA (DNA for which a function cannot be identified) than any other intracellular bacteria.

Calling the Wolbachia genome "a genetic dumping ground," Eisen an evolutionary biologist compared it to the human Y chromosome and the knot-like centromeres in the middle of eukaryotic chromosomes. "This strain of Wolbachia has evolved in a different way than other intracellular bacteria it appears that natural selection has been inefficient in this species, most likely because it repeatedly experiences very small population sizes," he says. "These population bottlenecks prevent natural sele
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Contact: Robert Koenig
rkoenig@tigr.org
301-795-7880
The Institute for Genomic Research
16-Mar-2004