Analysis of bacterial community structures in coastal sediments in the Ariake Sea

Bacterial communities in sediment samples at two sites in the Ariake Sea, Ashikari and Rokkaku, were investigated by double-gradient denaturing gradient gel electrophoresis (DG-DGGE) analysis and 16S rRNA gene (rDNA) sequencing analysis. Seasonal changes of the bacterial community structures were evaluated by cluster analysis using Ward's method from DG-DGGE profiles. The analysis indicated that the bacterial communities were more susceptible to a seasonal effect near estuarine areas than at offshore areas.addition, DG-DGGE and 16S rDNA sequencing analyses revealed a shared bacterial community of sediment samples at Ashikari and Rokkaku, comprising the phyla Actinobacteria, Bacteroidetes, Chloroflexi, Cyanobacteria, Firmicutes, Proteobacterla, and Verrucomicrobia.particular, 16S rDNA sequencing analysis showed that the annual detection rates of sul fate-reducing bacteria, including Desulfobacterium, Desulfomonile, Desulfonatronum, Desulfonema, Desulfosarcina, and Desulfonispora, fluctuated between 0-20% and 5-15% at Ashikari and Rokkaku, respectively. These fluctuations may alter the balance of the sulfur cycle in the Ariake Sea, and might be an indicator of further environmental change at the tideland.