Abstract
The diversity of soil green microalgae (Chlorophyta) is generally poorly known and likely underestimated because of their morphological poverty and crypticity. The use of molecular tools has revolutionized algal diversity research, including the discovery of numerous new taxa. On the basis of light microscopy, we isolated Chlorochytrium-like strain ACSSI 023 from gray forest soil (Moscow region, Russia), but with spongy rather than network chloroplast. This strain was evaluated by means of 18S rRNA gene and ITS2 sequences analyses and ultrastructural observations. Morphology, comparing the ITS2 secondary structure, compensatory base changes, intron lacking and percent similarity of the 18S rRNA gene of the isolated strain allowed us to propose a new genus and species for it, Spongiosarcinopsis terrestris gen. et sp. nov. The genus forms a separate independent branch within the Stephanosphaerinia clade (Chlorophyta, Chlorophyceae) with type species—Spongiosarcinopsis terrestris ACSSI 023.