Molecular characterization of the planktonic microorganisms in water of two mountain brackish lakes

The prokaryotic diversity in two brackish lakes (Sayram Lake and Chaiwopu Lake) was investigated by constructing bacterial and archaeal clone libraries of 16S rRNA genes. Bacterial clones from Sayram Lake were classified into six phyla (Proteobacteria, Verrucomicrobia, Bacteroidetes, Planctomycetes, Acidobacteria, Actinobacteria). Of these, Proteobacteria and Verrucomicrobia were the most dominant, representing 50.4 and 16.8% of the clone library, respectively. Sequences related to Proteobacteria (58.1%), Cyanobacteria (17.2%), Bacteroidetes (15%), Verrucomicrobia (4.3%), Actinobacteria (3.2%) constituted over 97% of the bacterial clone library from Chaiwopu Lake. In addition, 58.8% (Sayram Lake) and 48% (Chaiwopu Lake) of bacterial clones showed high sequence identity to pure cultures. The composition of Archaea was obviously different between the two lakes. Only the Crenarchaeota phylum was found in the Sayram Lake, whereas Archaeal sequences from Chaiwopu Lake were classified into three phyla: Crenarchaeota (5.8%), Thaumarchaeota (81.2%), and Euryarchaeota (13%). Among the archaeal sequences, 94.2% were highly related to cultivable species of the genus Nitrosopumilus, Methanoculleus, and Methanobacterium. These results showed a high diversity of potential cultivable heterotrophic bacteria in Sayram Lake and Chaiwopu Lake. Chaiwopu Lake was a source of potentially novel, cultivable archaea.