Genomic Survey of a Hyperparasitic Microsporidian Amphiamblys sp. (Metchnikovellidae).

Metchnikovellidae are a group of unusual microsporidians that lack some of the defining ultrastructural features characteristic of derived Microsporidia and are thought to be oneof their earliest-branching lineages. The basal position of metchnikovellids was never confirmed bymolecular phylogeny in published research, and thus far no genomic data for this group were available. In this work, we obtain apartialgenomeof metchnikovellidAmphiamblys sp.using multiple displacement amplification, next-generation sequencing, and metagenomic binning approaches. The partial genome, which we estimate to be close to 90% complete, displays genome compaction on par with gene-dense microsporidian genomes, but contains an unusual repertoire of unique repeat elements. Phylogenetic analyses of multigene datasets place Amphiamblys sp. as the first branch of the microsporidian lineage following the divergence of amitochondriate microsporidian Mitosporidium. We find evidence for amitochondrial remnant presumably functionally equivalent to a mitosome in Amphiamblys sp. and the common enzymatic complement for microsporidian anaerobic metabolism. Comparativegenomicanalyses identify the conservationof components for clathrin vesicle formationasoneof thekey features distinguishing themetchnikovellid from its highly derived relatives. The presented data confirm the notion of Metchnikovellidae as a less derivedmicrosporidian group, and provide an additional stepping stone for reconstruction of an evolutionary transition from the early diverging parasitic fungi to derived Microsporidia. [ABSTRACT FROM AUTHOR]