SEASONAL DYNAMICS AND PHYLOGENETIC ANALYSIS OF BACTERIOPLANKTON IN LAKE ERNAI, SW-CHINA

The community composition and seasonal variation of bacterioplankton were investigated using 16S rRNA gene sequence analysis in high mount Lake Erhai, China. Restriction fragment length polymorphism (RFLP) analysis revealed remarkable seasonal fluctuations in bacterio-planktonic composition. A total of 1498 clones were obtained from 16 water samples, and most of clones belonged to the clusters alpha-Proteobacteria, beta-Proteobacteria, gamma-Proteobacteria, Actinobacteria, Bacteroidetes, Verrucomicrobia, and Cyanobacteria. Among these groups, alpha-Proteobacteria was the identified as most dominant group in spring and summer. However, the structure shifted toward a beta-Proteobacterium-dominant community in autumn and winter. The clone libraries were found having the greatest diversity in winter, and some species only appeared in their specific seasons. The number of operational taxanomic uints (OTUs) predicted for the Lake Erhai ranged from 42.7 to 98.0, significantly lower than the samples from low-altitude lakes. The results of partial redundancy analysis (RDA) showed that environmental factors associated with nitrogen could play an important role in driving the conversion of two major groups in Lake Erhai. The present study indicated that the bacterio-plankton communities of Erhai Lake were similar to other freshwater ecosystems as many sequences showed 93.8% - 100% homology with known sequences found in other freshwater ecosystems, but had many unique characteristics. And also part of communities predicted to be from marine ecosystems.These findings provided fundamental and specofic information on the structure of bacterioplankton and the microfood web in Lake Erhai.The community composition and seasonal variation of bacterioplankton were investigated using 16S rRNA gene sequence analysis in high mount Lake Erhai, China. Restriction fragment length polymorphism (RFLP) analysis revealed remarkable seasonal fluctuations in bacterio-planktonic composition. A total of 1498 clones were obtained from 16 water samples, and most of clones belonged to the clusters alpha-Proteobacteria, beta-Proteobacteria, gamma-Proteobacteria, Actinobacteria, Bacteroidetes, Verrucomicrobia, and Cyanobacteria. Among these groups, alpha-Proteobacteria was the identified as most dominant group in spring and summer. However, the structure shifted toward a beta-Proteobacterium-dominant community in autumn and winter. The clone libraries were found having the greatest diversity in winter, and some species only appeared in their specific seasons. The number of operational taxanomic uints (OTUs) predicted for the Lake Erhai ranged from 42.7 to 98.0, significantly lower than the samples from low-altitude lakes. The results of partial redundancy analysis (RDA) showed that environmental factors associated with nitrogen could play an important role in driving the conversion of two major groups in Lake Erhai. The present study indicated that the bacterio-plankton communities of Erhai Lake were similar to other freshwater ecosystems as many sequences showed 93.8% - 100% homology with known sequences found in other freshwater ecosystems, but had many unique characteristics. And also part of communities predicted to be from marine ecosystems.These findings provided fundamental and specofic information on the structure of bacterioplankton and the microfood web in Lake Erhai