Aerofilum fasciculatum gen. nov., sp. nov. (Oculatellaceae) and Euryhalinema pallustris sp. nov. (Prochlorotrichaceae) isolated from an Indian mangrove forest

Two novel cyanobacteria (AP3 and AP3b) with thin cells and simple morphology were isolated from two islands of the In-dian Sundarbans. The 16S rRNA phylogeny data revealed the distinct lineage of AP3b which was nearest to the clade incor-porating the genus Oculatella and Tildeniella. Strain AP3 shared a common ancestor with the species Euryhalinema man-grovii. Additionally, the novel 16S rRNA gene sequences of strains AP3 and AP3b showed similarities about 98% and 93% respectively compared to those of established genera or species to which they were phylogenetically related. Furthermore, the folding patterns of semi-conservative structures like D1-D1', Box-B and V2 helices of 16S-23S ITS region for both strains AP3 and AP3b displayed significant variations and uniqueness when compared with their respective reference strains (Euryhalinema mangrovii for AP3 and all the genera of Oculatellaceae for AP3b). Strain AP3 shared similar morphological features with its reference strain which confirmed its inter-species relationship. The diagnostic features of AP3b including the presence of necridic cells, aerotopes and a cluster-like growth pattern were found to be very contrasting. Altogether, these results substantiated the establishment of strain AP3b as a novel mono-specific genus named Aerofilum fasciculatum and strain AP3 as the second novel species under the genus Euryhalinema, referred to as Euryhalinema pallustris.

Automated summary

The study isolated two novel cyanobacteria, AP3 and AP3b, with AP3b being established as a new mono-specific genus named Aerofilum fasciculatum, and AP3 identified as the second novel species under the genus Euryhalinema, referred to as Euryhalinema pallustris. These two cyanobacteria showed significant individual differences and uniqueness in 16S rRNA phylogeny data and folding patterns of semi-conservative structures.