Bacterial Diversity And Phylogeny In The Sediment Of Eutrophic East Lake, Wuhan

Aquatic eutrophication has become one of the major factors, which seriously impacts on the ecological security, economic and social development of China. Microbes as the decomposers in water ecosystems play an important role in the metabolism of nitrogen and phosphorus nutrients. However, studies on the communitiy structure and diversity of microbial in eutrophic waters by using molecular ecological technology are still few in China. Moreover, the studies on specific functional groups of microbes were even fewer. Therefore, it is very important to study the diversity, distribution and function of the microbes, especial the functional microbial community in the eutrophic waters.East Lake in Wuhan City, China is a typical eutrophic lake. The sediment samples were collected by five-point sampling method from its four typical sub-lake, Guozheng Lake, Tangling Lake, Tuan Lake and Miao Lake in September, 2009. Based on clone libraries, restriction fragment length polymorphism (RFLP) method and sequencing analysis, bacteria community structure and diversity were investigated. Moreover, the phylogeny diversity of the nirS-denitrifiers communities in the sediments was also studied. The main results are listed as follows:1. Bacterial diversity and phylogeny in the sediments of the eutrophic East Lake.⑴Environmental parameters showed that the sediment from Miao Lake (M site) contained the highest amount of total nitrogen (TN) and NH₄⁺-N, while that from Tuan Lake (T site) contained the lowest. The diversity, richness and evenness statistics calculated by DOTUR software indicated that among the four sub-lakes, Tuan Lake harboured the highest diversity and richness, while Miao Lake had the lowest. The results suggested that the diversity indices of the bacteria community were probably affected by the content of TN and NH₄⁺ nutrients in the sediments.⑵NJ tree constructed by using the PHYLIP software showed that a high diversity of microbe species inhabited in the Donghu sediments. Pylogenetic analysis determined at the phlum level has divided them into the phyla of Proteobacteria, Acidobacteria, Bacteroidetes, Chloroflexi, Firmicutes, Verrucomicrobia, Planctomycetes, Crenarchaeota and Euryarchaeota. Phyla like Proteobacteria, Acidobacteria, Bacteroidetes, Chloroflexi, Firmicutes and Verrucomicrobia were present in all 4 sampling sites. However, Planctomycetes was absent from site T, and Archaea (Crenarchaeota and Euryarchaeota) were only found in sediment samples of M site. Statistics indicated thatδ-Proteobacteria,β-Proteobacteria,γ-Proteobacteria, Acidobacteria and Verrucomicrobia were the dominant microorganisms.⑶BLAST results sugguested that the microbial community in the sediments of East Lake was similar to those from various habitats, especially from the eutrophic Dongping Lake and Honghu Lake in China.2. Genetic diverisy and phylogeny of nirS-denitrifiers in the eutrophied Donghu Lake⑴The diversity and richness indices showed that among the four sub-lakes, Tuan Lake (T site) harboured the highest diversity and richness of NirS-like denitrifiers, while the denitrifiers in Miao Lake (M site) was the lowest. Coupled with the environmental factors determined, it was suggested that the diversity indices was affected by the content of TN, NH₄⁺ and NO₃^- nutrients in the sediments.⑵Phylogenic analysis suggested that sedimentary NirS-like denitrifiers in the East Lake could be classified into three groups, GroupⅠ,Ⅱ,Ⅲ. GroupⅠaccounted for 67.7% of all tested communities. 81% sequences from Guozheng Lake were clustered into GroupⅠ, while 67.7% sequences from Miao Lake were clustered into GroupⅡ.⑶Comparative analysis of communities from East Lake and artificial wetland found that they were closely phylogenetically related. It indicated that GroupⅠandⅡmight play an important role in the denitrification in the eutrophied lakes.