Diversity Of Planktonic Bacteria And Archaea In Huguangyan Maar Lake

Numerous planktonic bacteria are widely distributed in aquatic ecosystems. They have high genetic diversity and the capacity of living in almost complex environment on earth. Their community structures play an important role in ecosystem cycles. Here we based on the culture-independent and culture-dependent methods, aiming to study the planktonic bacterial diversity in a typical Maar lake-Hugangyan and furthermore, address its seasonal changes.Our work incledes the analysis of bacteria isolations, culturing by two types of common medium, and the construction of 10 gene clone libraries, being constructed with the lake's main microbial communities. As for the analysis of isolations, we use the BOX-PCR technique to type the various ones.First, we chose the center vertical watermass of Lake Huguangyan, one of the deepest site, as its typical region and investigated the microbial diversities on 1m, 5m and 13m water layers, respectively, in summer and winter. First of all, 340 bacterial strains were obtained by culturing on R2A medium and agar medium that were prepared by filtered lake water and agar. Then,for the analysis of BOX-PCR we extracted the DNA from each strain by alkaline lysis. Next, strains were distinguished by manual screening on different bands. Later, RDP data analysis showed that 340 strains belonged to Proteobacteria, Actinobacteria, Firmicutes, Bacteroides, which are the main microbial categories in lakes. We found that the proportion of types of bacteria was inconsistent in different seasons, water levels and mediums. But at the same time Proteobacteria is constantly as a superior, occupying more than 76% of the total number of bacteria. In addition, the results of the analysis reveal that Bacteroides was only found in winter samples. The data by BLAST comparison of 16S rRNA genes showed that various types of bacterial 16S rRNA homology are above 90%, excepting the strains of the summer sample from agar medium and R2A medium:Shui5-7, Shui5-12, Shui13-6, Shui13-11, R13-5, R13-7 and dS1-1, dS5-26, dR1-11, dR1-21 in winter. They are not exceeding 90% homology, which may represent a new species in the correspondent categories.Secondly, in addition to the analysis of bacterial diversity by culture-dependent methods, we also employed culture-independent methods to study the diversity. By using 10 categories of universal primers, we constructed 10 clone libraries of 16S rRNA, including Archaea, Bacteria, Actinomycetes, Firmicutes, Cyanobacteria, Bacteroides, Planctomycetes,α-Proteobacteria,β-Proteobacteria andγ-Proteobacteria. The results revealed different characteristics with the above culturing results. And sequences of Archaea and Planctomycetes were only cloned in these libraries. Besides, there are some more new sequences of other categories from the libraries. The value is 6/30 in Archaea, 8/30 in Bacteria, 2/30 in Actinomycetes, 2/30 in Firmicutes, 23/30 in Planctomycetes, 29/30 in Bacteroides, 3/30 in Cyanobacteria, 8/30 inα-Proteobacteria, 11/31 inβ-Proteobacteria, 27/31 inγ-Proteobacteria, respectively.