Three strains of Nostoc-related morphotypes isolated from Geum River, Korea. They were studied based on a polyphasic approach using morphology, ecological and molecular data. Phylogenetic analysis of 16S rRNA gene revealed that the selected eight genera were clearly separated into each taxonomic group, and in them, Korean strains formed a clade with Aliinostoc spp. The Aliinostoc sensu lato were monophyletic but divided two distinct lineages with high genetic distance between them (4.2% p-distance between clades vs. 1.8% within clades). In accordance with the statistical analysis, the Korean strain-belonging clade was significantly divergent to segregate from other Aliinostoc clades compared to those of the relative genera (2.8% p-distance between sister-genera vs. 0.9% within the same genus). In addition, the ITS rDNA sequence of the Korean strains showed unique characteristics in terms of nucleotide compositions and length in comparison to that of the Aliinostoc, including their secondary structures of D1–D1ʹ and Box-B. These results supported the establishment of a new genus, proposing Pseudoaliinostoc gen. nov. with a description of P. sejongens sp. nov. for the Korean strains. Likewise, three previously described Aliinostoc species were proposed to be transferred to P. soli comb. nov., P. tiwarii comb. nov., and P. constrictum comb. nov.

Porphyrosiphon annulatus sp. nov. belonging to Microcoleaceae, Oscillatoriales was collected from the moist soil under the rock in the Gwanggyo Mountain of Suwon City, Gyeonggi Province, Korea and cultured. Using the raw and cultured samples of the collected strains, we observed their morphological features through LM and TEM. Furthermore, their 16S rRNA gene and 16S–23S rRNA intergenic transcribed spacer (ITS) sequences were determined to be used phylogenetic analyses. We affirmed that thick sheath of the cells possessed transversely annular and longitudinal lamellations. The ultrastructure of thylakoids was a radial arrangement, which corresponds with a characteristic of the Microcoleaceae. In addition, P. annulatus displays the most similar morphology with type species P. notarisii; however, it differently holds the transversely annular lamellations with a shorter cell length and relatively dense trichome. Our 16S rRNA gene phylogeny showed that P. annulatus formed a clade with P. notarisii, and their DNA similarity was calculated to be 96.2%. The family Microcoleaceae was found to be paraphyletic with a distinct linage of the genus Porphyrosiphon. The ITS sequence of P. annulatus was unique in length and nucleotide composition, with different secondary structures of D1–D1ʹ and Box-B helices compared to those of close relatives. Overall, morphology and genetic traits of the Korean Porphyrosiphon suggest that P. annulatus should be considered to be a novel species.

Two strains of subaerial cyanobacteria were collected from two locations of the Republic of Korea, one in Seoul and the other in Gyeonggi-do, both of which were studied using morphological and molecular traits. The genus Edaphophycus belonging to the family Coleofasciculaceae is morphologically very similar to the type genus Coleofasciculus and genus Kastovskya. However, in genera Coleofasciculus and Roseofilum thylakoids were reported as radial arrangements, whereas in genera Anagnostidinema, Geitlerinema, Kastovskya, and Wilmottia, belonging to family Coleofasciculaceae, thylakoids were reported as parietal arrangements, and in genus Edaphophycus in this study, thylakoids also appeared as parietal arrangements. Phylogenetic analysis of 16S rRNA showed that our two Edaphophycus epilithus strains clustered in the same clade, forming a sister relationship with genus Anagnostidinema. This suggested that our species belongs to the family Coleofasciculaceae. In addition, the ITS structure of E. epilithus showed different features when compared with genera Coleofasciculus and Anagnostidinema. These results demonstrated that E. epilithus sp. nov. is unique in morphology and molecular traits. Therefore, we propose this to be a novel species belonging to family Coleofasciculaceae and genus Edaphophycus gen. nov.