Abstract:

Marine bacteria are an extremely important component of marine bioresources. We studied the community structure and diversity of cultured and uncultured bacteria in surface layer sediment sampled from the East China Sea (122°10′41″ E, 29°49′7″ N) by buried piece observation, fluorescence enumeration, pure culture techniques and 16S rDNA clone library analysis. The average abundance of bacteria was (9.30±3.44)×10⁷ cells/g according to fluorescence microscopy enumeration and observation of buried slides. A total of 313 bacterial strains belonging to 20 genera was obtained from four kinds of culture medium and the separation efficiency of bacteria ranked as RO>M1>Zobell 2216>MR2A. In terms of morphology, physiology and biochemistry, Bacillus (21.08%) and Marinococcus (17.25%) were shown to be the most dominant and highly diverse bacteria. The analysis of 16S rDNA sequence from 73 representative bacteria showed most clones were affiliated with Firmicutes (57.5%): the other marine bacteria including gamma-Proteobacteria (32.9%), Flavobacteria (4.1%), and Actinobacteria (5.5%). Most clones were related to uncultivated bacterial clones retrieved from surface layer sediment and contained several highly divergent 16S rDNA gene sequences. After constructing a molecular library and phylogenetic analysis, the sequenced clones were shown to fall into two phyla of the domain Bacteria, Firmicutes and Proteobacteria, in which Bacillus and gamma-proteobacteria were the dominant groups, respectively. The results revealed that the species and community structure of bacteria in surface layer sediment from the East China Sea continental shelf were abundant and diverse, thus warranting further research and exploitation.

Key words: East China Sea, bacteria, 16S rDNA, community structure, diversity