Insights into the phylogeny of false-branching heterocytous cyanobacteria with the description of Scytonema pachmarhiense sp. nov. isolated from Pachmarhi Biosphere Reserve, India

Abstract

A false branching cyanobacterium (strain 10A1_PS) was isolated from a freshwater body of the Pachmarhi Biosphere Reserve, India and was characterised using the polyphasic approach. The detailed morphological examination indicated that the strain belonged to the complex genus Scytonema as it exhibited typical false branching character whose frequency increased with age of the culture. As the family Scytonemataceae and the genus Scytonema has been shown to be polyphyletic in many studies, we provide deep insights into the phylogenetic complexities within the family Scytonemataceae based on 16S rRNA gene phylogeny along with complete morphological, molecular and phylogenetic characterisation of the strain. The 16S rRNA gene phylogenetic tree inferred by Bayesian Inference, Neighbor-Joining and Maximum Parsimony methods showed that the strain clustered within the Scytonema sensu stricto clade. The phylogenetic distance and the positioning of the strain clearly indicated it to be different from other Scytonema species. Further analysis using rbcL phylogeny, folded secondary structures of the 16S-23S ITS, p-distance and percentage pairwise similarity matrix clearly distinguished the strain 10A1_PS from the other closely related species. In accordance with the International Code of Nomenclature for Algae, Fungi and Plants, we propose the name of the new species to be Scytonema pachmarhiense.