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Two cyanobacterial strains morphologically identified to the genus Nostoc were isolated from a wet rocky wall in a mid-subtropical region in China, and they were taxonomically and phylogenetically characterized based on the polyphasic approach combining morphological and genetic characteristics. 16S rRNA gene sequence analysis showed that the two strains containing six clones were all >99.6% similar to each other, but had < 94.3% similarities to the existing cyanobacterial genera. The phylogenies based on 16S rRNA and rpoC1 gene sequences indicated that their sequences grouped into a unique and robust cluster with high bootstrap values. This unique cluster was separated from the clade of the 'Nostoc sensu stricto' and the respective clades formed by the morphologically similar genera Mojavia, Desmonostoc, Aliinostoc, Komarekiella and Halotia. The 16S-23S rRNA ITS secondary structure of the both strains exhibited the unique pattern of D1-D1´, Box-B and V3 helix, distinguishing it from the other heterocytous genera. Such a clear cluster leads to the establishment of Minunostoc gen. nov., with the type species as Minunostoc cylindricum sp. nov.

Desertifilum, a filamentous cyanobacterial genus, was initially described from biological crusts in Thar crusts in India. In this study, we isolated a novel cyanobacterial strain (CHAB7200) from a alkaline pool in Zhejiang province, China. The strain showed an identical 16S rRNA gene sequence to Desertifilum tharense, but was distinctly different in cellular morphology, ultrastructure and ecology. In addition, the strain exhibited growth ability at different alkalinities during 4.5 ~ 54 g/L, and the optimum growth was shown at 1% salinity, indicating its stronger tolerance to wider range of alkalinities and salinities than D. tharense. Ecological niche is an important criterion used to separate and define cyanobacterial species. In this case, the strain was proposed as a novel cyanobacterial species, Desertifilum salkalinema. sp. nov.