Microsporidia: Eukaryotic Intracellular Parasites Shaped by Gene Loss and Horizontal Gene Transfers.

Microsporidia are eukaryotic parasites of many animals that appear to have adapted to an obligate intracellular lifestyle by modifying the morphology and content of their cells. Living inside other cells, they have lost many, or all, metabolic functions, resulting in genomes that are always gene poor and often very small. The minute content of microsporidian genomes led many to assume that these parasites are biochemically static and uninteresting. However, recent studies have demonstrated that these organisms can be surprisingly complex and dynamic. In this review I detail the most significant recent advances in microsporidian genomics and discuss how these have affected our understanding of many biological aspects of these peculiar eukaryotic intracellular pathogens.