Maricoleus vaginatus gen. et sp. nov. (Oculatellaceae, Synechococcales), a novel cyanobacterium isolated from a marine ecosystem in China

Cyanobacteria are widely distributed prokaryotes that play important roles as primary producers in diverse ecosystems. However, taxonomic studies focusing on cyanobacteria from marine ecosystems are rarer than those dealing with cyanobacteria from freshwater environments. In this study, a strain of Leptolyngbya- like filaments was isolated from colonies attached to the aquatic weed Acorus calamus in Xincun Port, Hainan Province, China. The strain (named WZU 0102) was examined using the polyphasic approach, i.e. the combination of morphology, ultrastructure, phylogeny of 16S rRNA gene and ITS secondary structures. Although this newly isolated strain was found to be morphologically similar to members of the genus Leptolyngbya based on light microscopic observations, phylogenetic analysis revealed the strain to be distant from Leptolyngbya sensu stricto, forming an independent branch with certain taxonomically ambiguous Leptolyngbya-like strains in the constructed phylogenetic trees. The analyses of ITS secondary structures also distinguished the WZU 0102 strain from other related genera. On the basis of these findings, a novel genus Maricoleus with type species Maricoleus vaginatus is established and described herein. Moreover, two similar Leptolyngbya-like strains isolated in Brazil are re -identified as Maricoleus vaginatus. Our findings in this study not only expand the currently limited taxonomic coverage of marine cyanobacteria but also contribute to a taxonomic revision of Leptolyngbya-like cyanobacteria.