Microorganisms colonizing surface in coastal marine water as revealed by 16S rRNA gene clone library analysis

To investigate the community structure and dynamics of surface-associated microbial cells, sterile strengthened glass sheets were immersed in near-shore marine water of Xiamen, China. The organisms colonizing the glass surface were sampled after 1 h, 7 and 14 days. Three 16S rRNA gene clone libraries were constructed using primers universal for the domain bacteria. 40 clones were selected randomly from each clone library for sequencing, and the sequences were submitted for homology and phylogenetic analyses. All cloned sequences fell into 6 major groups: Sequences of clones originating from chloroplasts of eukaryotic Bacillariophyta were abundant in all three samples (ranging from 16 to 64%) and predominated in 7 and 14-day samples and occupied 45% of the total cloned sequences; γ-Proteobacteria came next and occupied 42% of the total sequences and the proportion of γ-Proteobacteria in each clone library decreased with immersion time. An entophytic bacterium Serratia proteamaculans involving biofilm formation was predominant within the γ-Proteobacteria and took up more than half of the clone library of 1 h sample. Other bacterial groups, Bacteroidetes, α-Proteobacteria, Firmicutes and Cyanobacteria occupied 5 to 1%.   Key words: Microorganisms colonization, dynamics, 16S rRNA, clone library, marine coastal water.