Dissertation > Biological Sciences > Microbiology > Microbial ecology and geographical distribution

Comparison of Genetic Diversity of Total Planktonic Bacteria and Active Planktonic Bacteria in Huguangyan Maar Lake in Summer

Author GuoZuoRu
Tutor WuZaoHe
School Guangdong Ocean University
Course Aquaculture
Keywords Maar Lake(Hu Guangyan) Planktonic bacteria Active planktonic bacteria 16S rDNA ITS rpoB Vibrio Genetic diversity Phylogenetic analysis
CLC Q938
Type Master's thesis
Year 2011
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Planktonic bacteria are the most abundant microbes and widely distributed in aquatic ecosystem. They participate in material and energy metabolism and thus play a significant role in aquatic ecosystem. Hu Guangyan Maar Lake is a special kind of Crater Lake with old geological ages that makes it different from other lakes. Therefore it is valuable to research and develop microbial resources in Maar Lake. We investigated the genetic diversity of planktonic bacterial and active planktonic bacterial through constructing seven clone libraries of common lake microbial groups. Meanwhile, we used culture-depend method to study the genetic diversity of Vibrio.We chose one of the deepest sites and gather samples from three water layers (1 m, 5 m, and 13 m). Then we employed universal primer to amplify 16S rDNA from total DNA and total RNA from planktonic bacteria, respectively. Positive clones were chosen for sequencing. RDP analysis showed that all 414 sequences were classified into 15 phylums, 32 orders and 52 families. Four kinds of Proteobacteria (α-、β-、δ-、γ-Proteobacteria) were found in Maar Lake. Nearly half of the sequences were affiliated with Alphaproteobacteria, which was the most abundant group followed by Verrucomicrobia and Bacteroidetes. The depth might cause diversity discrepancy of planktonic bacteria. The diversity of planktonic bacteria in surface (1 m) seemed higher than bottom (10 m). The diversity of total planktonic bacteria is slightly higher than that of active planktonic bacterial in surface. The diversity of active planktonic bacterial is obviously higer than total planktonic bacteria in 10m. We got a clone of the OD1and Spirochaetes sequence that is the first time to be reported in domestic and foreign research of lake diversity.Seven universal primers were used to amplify 16S rDNA from the same environmental samples in order to analyze the difference of diversity in group levels. We constructed seven clone libraries of common microbial groups of lakes: Planctomycetes, Alphaproteobacteria, Betaproteobacteria, Gammaproteobacteria, Bacteroidetes, Firmicutes, and Actinobacteria. The results showed that the diversity of planktonic bacteria was different within different libraries and depths.Finally, we isolated vibrio. strains from Maar Lake by culture-depended method and compared them with those from Zhanjiang port nearby. By analysis of the sequences of ITS, most sequences (18 in 19) from port of Zhanjiang were affiliated to Vibrio while no sequences belonged to Vibrio. in isolates from the Maar Lake. All sequences amplified with rpoB gene suggested that the bacterial selected by TCBS from Zhanjiang port were all Vibrio. The use of ITS and rpoB gene as molecular markers for classification and identification of bacteria were basically the same in genus level but notable differences in species level.

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