Unsuspected findings about phylogeny and ultrastructure of the enigmatic cyanobacterium microcrocis geminata resulted in its epitypification and novel placement in geminocystaceae

Abstract

The genus Microcrocis belongs to long ago established cyanobacterial taxa for which relevant data required for a modern taxonomic analysis remained unknown for a long time. In present study we proposed an epitype originating from a large natural population of the type species M. geminata. Through isolating clean individual colonies from the environmental sample, sufficient material for a single colony PCR and amplification of genomic DNA by MDA method was obtained. Molecular analyses of the 16S rRNA gene determined the unsuspected position of the cyanobacterium within the family Geminocystaceae, forming a distinct branch with two Merismopedia sequences. 16S rRNA and ITS analysis clearly separated the two taxa on generic level. The phylogenetic classification is conspicuously consistent with the ultrastructure of parallel thylakoids unique for some members of the family Geminocystaceae. Distinctive morphology of the genus including typical longitudinal division is discussed.