[Studies on the actinobacterial diversity in aiding lake sediments].

OBJECTIVE: This study aims at investigating the diversity of actinobacteria in Aiding Lake, a hypersaline lake and the lowest land point in China. METHODS: The diversity of actinobacteria in the sediment from Aiding Lake was investigated by culture--independent method based on phylogenetic analysis of 16S rRNA gene sequences and selective isolation. Specific primers were used to amplify the actinobacterial 16S rRNA gene, and corresponding clone libraries were constructed for the sediment samples. Different clones selected on the basis of Hae III digestion patterns were sequenced. Nine selective media with different salinities were used to isolate actinobacteria from the sediment samples. RESULTS: The analysis of 16S rRNA gene sequences showed that 273 clone sequences belonged to subclasses Actinobacteridae (208), Acidimicrobidae (13) and Rubrobacteridae (52). The dominant actinobacteria was genus Rothia, which accounted for 37% of total clones. The similarity between 45.8% of 273 detected sequences and published sequences were less than 97%, which might represent new taxa. Some sequences, which formed several distinct clades in phylogenetic tree may represent new taxonomical groups of actinobacteria. Fifty-five strains were isolated by different selective media. They belonged to six suborders of the order Actinomycetales, of which Streptomyces and Nocardiopsis were the dominant groups. Six potential new species were obtained. CONCLUSION: Aiding Lake harbors abundant actinobacteria, including large number of unknown actinobacterial groups.