Les microsporidies: un regain d'intérêt pour ces curieux parasites

Microsporidia were found to be involved in some diseases of insects (silkworm, bee, pests) and aquaculture pathology. They are important as opportunistic parasites in AIDS patients and are also prevalent in the European population (8 %). The cytological and molecular characterisation of numerous species infecting humans was determined. To obtain an easier diagnosis and more efficient therapy, researches were developed on the genome as well as on the invasive apparatus, which is unique in the living world. Recent, more important insights are the characterisation of polar tube proteins, the evidence for genome plasticity, and the size of haploid genome representing, for some species, the smallest nuclear genomes known so far. The placement of microsporidia in eukaryotic phylogenetic tree is still uncertain. They can be viewed as amitochondrial parasites which lost secondarily their mitochondria, and rDNA 23S or some protein sequences suggest a late origin within the terminal crown. The reduced size of the translation machinery could be a consequence of parasitism.