How microsporidia evolve

Genomes within a group of eukaryotic obligate intracellular parasites—the microsporidia—are changing very slowly, even as the genes within them are evolving at a "strikingly high" rate, according to a study in the latest edition of Current Biology. The evolution of eukaryotic genomes usually correlates with the rate of sequence evolution, but the results of this study show that genomes do not necessary evolve in a clock-like fashion, say the authors.

Patrick Keeling at the University of British Columbia and colleagues randomly sequenced 685,000 base pairs of the microsporidian Antonospora locustae genome. They compared the organization of 183 genes found there with the recently completed genome sequence of the distantly related human parasite Encephalitozoon cuniculi, also a microsporidium. The degree of conservation of gene order between the two species was measured as the percentage of gene couples—pairs of genes adjacent to each other—that were couples in both species.

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