Topographic effects of coastal seas on the composition of the culturable bacterial communities in marine sediments

Abstract

The influence of the topographical structure of natural coastal marine environments on the composition of culturable microbial communities in marine sediments was analyzed by comparing the composition of the culturable fraction of sedimental bacterial communities from five topographically disparate marine ecosystems. The sampling areas included open, enclosed and semi-closed coastal seas near Nagasaki, Japan. Bacterial identification and phylogenetic analyses based on 16S rDNA gene sequencing showed that 84.0% of the isolated strains belonged to known species. The marine indigenous γ-Proteobacteria were significantly higher (P < 0.05) in abundance among the strains isolated from the open coastal seas, but were less abundant in the enclosed and the semi-closed coastal seas. Conversely, the abundance of the low G + C gram-positive bacteria, mainly soil-derived Bacillus species, was significantly higher (P < 0.001) in the enclosed sea than in the open coastal seas. It was found that the composition of the culturable fraction of coastal sediment bacterial communities might be influenced by topographic factors and could be utilized as a microbiological tool for the assessment of the deterioration of environmental conditions in enclosed coastal seas.