| Submerged surfaces in marine environments are rapidly colonized by bacteria. These bacteria in nature play a key role in the production and degradation of organic matter, the degradation of environmental pollutants, and the cycling of limiting nutrients. Surface bacteria may have important influences on larval settlement in aquaculture, and also participate in biocorrosion and biofouling, causing substantial economical loss and damage in marine fishery and marine engineering. Although it is extremely important, very little is known about the community structure and dynamics of primary surface colonizers in coastal environments. To determine the bacterial diversity and community succession during early stages of surface colonization in coastal water of Qingdao, glass surfaces were incubated for 1 to 7 days and determined via bacterial 16S rDNA clone library analyses. A total 144 OTUs were sequenced from 269 clones of three clone libraries. 16S rDNA sequences phylogenetic analysis indicated that the bacteria fell into 8 major lineages: Proteobacteria (α-,γ- andδ-subdivisions), Bacteroidetes, Gemmatimonadetes, Firmicutes, Planctomycetes, Cyanobacteria, Actinobacteria and Acidobacteria. Our study shows that theα-Proteobacteria form one of the most common primary surface colonizers, along with theγ-Proteobacteria and Bacteroidetes within a week; the Roseobacter clade bacteria inside theα-Proteobacteria subdivision are ubiquitous colonizers of surfaces in coastal marine environments. Based on the cluster analysis, the 3 days′and 7 days′microbial assemblages are similar. These results are important in understanding the successional process of biofilm formation and in finding the strategies for biocorrosion prevention and control in marine environments.Nitrogen accumulation is a serious concern in aquaculture. Too much nitrite and ammonia are harmful because of its low transformation rate and high toxicity. Denitrifying bacteria have the ability of releasing excess nitrogen back to atmosphere in eutrophic aquaculture environments and enable the global nitrogen cycling. They play a central role in maintaining sustainable aquacultural systems. However, little is known about the denitrifying bacteria in aquaculture environments. To determine the structure and diversity of the denitrifying bacteria, a mariculture farm sediment was investigated for the first time. Five nirS gene libraries were constructed with a PCR-based clone approach. Subsequently, A total of 360 randomly selected nirS clones from the libraries were analyzed by restriction fragment length polymorphism (RFLP), and resulted in 158 operational taxonomic units (OTUs). We found taxonomically rich and novel communities from all these sequenced OTUs, with all nirS clones exhibiting less than 92% identity at the amino acid level to those of cultivated denitrifiers and other environmental clones in the database. Phylogenetic analysis of deduced amino acids grouped the nirS sequences into seven major clusters, and the nirS clones obtained in this study formed one major cluster. Only a few of the nirS clone sequences branched with those of known denitrifying bacteria. The results showed that nirS genes from the mariculture farm sediment and sequences from marine habitats all over the world indicated distinct denitrifier communities that grouped mostly according to their habitat. We suggest that these subgroups of denitrifiers had developed after selection through several environmental factors. These results may help us better understand the distribution of denitrifying bacteria, find beneficial denitrifiers, and study on the probiotics and bioremediation of aquaculture environments.
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