New genera of thin homocyted cyanobacteria from Brazilian tropical and subtropical marine islands

Brazil's Atlantic Ocean coast is approximately 7500 km long, with several coastal and oceanic islands. The cyanoflora of this area is not commonly included in published studies, resulting in an underestimated diversity. Here, we isolated and analysed through a polyphasic approach three strains of marine benthic homocyted cyanobacteria from Brazilian coastal islands with two distinct climates: ALCB 132761 and ALCB 132774 are from the tropics, and ALCB 132760 from the subtropics. These strains presented differences in their cell morphometry and presence/absence of sheath, but were similar in apical cell shape, colour, and form of the trichome. In the 16S rRNA phylogeny, Maximum likelihood (ML) and Bayesian posterior probability (PP) analyses placed our strains in two robust clades. We propose that Microlinema tropicalium gen. et sp. nov. (ALCB 132774) is placed in the Leptolyngbyaceae, and Insularia amadoi gen. et sp. nov. (ALCB 132761) and Salileptolyngbya insularis sp. nov. (ALCB 132760) in Pseudanabaenaceae. The 16S-23S Internal Transcribed Spacer (ITS) was used to reconstruct Box B and D1-D1' secondary structures, which were treated as autapomorphic characters. The new thin homocyted benthic cyanobacterial taxa described here from marine coastal islands of Brazil help to disentangle the Leptolyngbyaceae and Pseudanabaenaceae.