ABSTRACT
The term “microsporidia” is commonly used to describe a group of unicellular, small, obligate, intracellular, sporeforming organisms within the phylum Microsporidia, kingdom Fungi. Being true eukaryotes, microsporidia possess a membrane-bound nucleus and an intracytoplasmic membrane system and show chromosome separation on mitotic spindles. On the other hand, by possessing 70S ribosomes (with ribosomal subunits 30S and 50S containing prokaryote-sized 16S and 23S rRNAs [ribosomal RNAs] without separate 5.8S rRNA, which is considered as an important eukaryotic feature), simple Golgi membranes, relatively small genome (about 2-15 Mb), chitin, and trehalose in the spore wall, and by being free of mitochondria or peroxisomes, microsporidia resemble fungi (especially the zygomycetes).1 Recent phylogenetic analyses of the small-subunit (SSU) rRNA, the largest subunit of RNA polymerase II, TATA-box-binding protein, glutamyl tRNA synthase, α-and β-tubulin and mitochondrial Hsp70 (a heat shock protein or chaperonin) gene sequences in microsporidia provide further evidence that microsporidia and fungi are close relatives, which may have similarly evolved degeneratively from higher forms.2,3 An extensive phylogenetic analysis using eight genes placed microsporidia within the fungal clade, as a sister to a combined ascomycetes and basidiomycetes clade.4
