Genetic Diversity of Filamentous Cyanobacteria from Shore Regions of Okinawa

Abstract

Benthic marine cyanobacteria are ubiquitous oxygenic photosynthetic bacteria and they form major components of various communities, including epiphytic, epilithic and microbial mats, in coral reef environments. Filamentous groups may form almost monospecific macroscopic colonies, and sometimes make potentially harmful algal blooms (HABs). HABs bring serious problems for marine tourism but marine filamentous cyanobacteria are good resource for drug discovery. However, cultivation and identification of such filamentous cyanobacteria are difficult and there are taxonomic confusions. In this study, we investigate 17 samples from coral reef area of 10 localities in Okinawa. Macroscopic mats or cushions of filamentous cyanobacteria were collected. The samples were divided into three parts: (1) for morphological observation, (2) for molecular work, and (3) cultivation for further study. Dominant cyanobacteira of each sample identified morphologically as Anabaena, Hydrocoleum, Lyngbya, Oscillatoria, Phormidium, Schizothrix and Symploca. Molecular results of partial 16S rDNA sequences revealed six groups that composed of heterocystous group, Leptolyngbya group, Symploca group, Moorea group, Oscillatoria group and unknown group, respectively. Some samples corroborated between morphology and molecular results but some were not. In addition, four out of six groups closely related with natural product producers. These results suggest that there are high biodiversity of marine benthic filamentous cyanobacteria in Okinawa that may become seeds of HABs as well as providing promising resources for drug discovery.