Phylogenetic relationships of microsporidia and their ATP transporters. (a) Phylogenetic reconstruction of the microsporidian phylogeny based on available α- and β-tubulin amino acid sequences and gains of ATP and ABC transporters. Known genome sizes and number of transporters are shown. Ent. bieneusi tubulins cluster as a sister group to the clade including Encephalitozoon and Nosema species; this position is represented by a black square. (b) Evolution of the ATP transporter family based on available amino acid sequences from a range of microsporidian parasites. 1, Putative ancestral duplication of ATP transporters within the microsporidia following lateral gene transfer from prokaryotes. 2, A putative secondary gene duplication occurred in the more diverged genera, Nosema, Enterocytozoon and Encephalitozoon. 3, Supported lineage including all three diverged genera. 4, Species-specific duplication of an ATP transporter. *Data from NC, JFP et al., unpublished.