Community Diversity Of Microorganisms In Xizi Lake Determined By Culture-independent Methods

As major participant in nutrient circulation and energy flow, microorganisms play an important role in ecology and environment of lake. In tradition, the microorganisms were isolated and determined by culture-dependent methods. Only about 1% of microorganisms could be cultured in laboratory condition, so isolation and identification of microorganisms using culture-dependent is not sufficient With the development of molecular biology, large amount of analytic methods were invented. In order to understand the ecology and environment of Xizi Lake more clearly, we studied the structure of microorganisms in this area using culture-independent methods.Water sample were collected from 5 spots in Xizi Lake. After DNA extraction, 16S rDNA of all microorganisms was collect by PCR reaction. Via Ligated and converted 16S rDNA into DH5αE.coli, microbial 16S rDNA library was established. Positive clones were selected out and their DNA was sequenced. The sequences were further compared with the know sequences from database with BLAST program. By using DNAMAN package, 16S rDNA phylogenetic trees were constructed and analyzed in detail.The result showed the diversity of microbial 16S rDNA library. Among 27 clones, 9 clones match to low (G+C) % Gram positive bacteria, they are Bacillus subtilis, Staphylococcus saprophyticus, Streptococcus porcinus, Brevibacillus brevis, Bacillus sphaericus, Staphylococcus cohnii, Bacillus thuringiensis, Staphylococcus epidermidis and Bacillus simplex respectively; 6 clones closely relate toγ-proteobacteria, they are Pseudomonas alcaligenes, Escherichia coli, Shigella sonnei, Acinetobacter johnsonii, Pseudomonas putida and Proteus mirabilis respectively, 3 clones match toα-proteobacteria, they are Sphingomonas paucimobilis, Ochrobactrum lupin iand Agrobacterium rhizogenes; 2 clones belong to Actinobacteridae, they closely relate to Brevibacterium casei and Micrococcus luteus; 3 clones belong to Cyanobacteria, one clone is similar with Leptolyngbya nodulosa, the other two are Uncultured Cyanobacterium; in addition, in those 27 clones, 3 clones are not bacteria but eukaryotes, they have similar sequence with Dinophysis norvegica, Ditylum brightwellxi and Nitzschia frustulum respectively, Besides, one clone maybe is a 16S rDNA of Uncultured bacterium.