The diversity of cyanobacteria from the semi-arid region of Rajasthan, India, remains vastly unexplored and warrants systematic investigation. We isolated two cyanobacterial strains (SN2022/33 & AT2016/25) of non-heterocytous, filamentous cyanobacterium from samples of sandy soil biological crusts and investigated them using a polyphasic approach. Based on 16S rRNA gene sequence identity, both strains formed a distinct lineage, with 16S sequence identity (p-distance) < 95% to the closest sister genera Trichocoleus, Venetifunis, Trichothermofontia, and Pinocchia. Analyses of 16S-23S Internal Transcribed Spacer (ITS) secondary structures (D1-D1′, BoxB, and V3 helixes) yielded substantial differences from phylogenetically associated taxa. Morphologically, both strains corresponded to members of the family Trichocoleusaceae (Leptolyngbyales), with tapered filaments and conical-pointed end cells. Most significantly, this taxon exhibited a form of true branching, with prolific unilateral or bilateral extrusions, something that had previously been the exclusive purview of members of the Nostocaceae. The combined evidence from conventional and molecular studies supports the recognition of the isolates as a novel taxon hereby described as Edaphifilum ginni gen. et sp. nov., in accordance with the International Code of Nomenclature (ICN) for Algae, Fungi, and Plants.
Tomer et al. (Wed,) studied this question.