Studies On The Actinobacterial Diversity In Aiding Lake Sediment

Actinomycetes from salt environment is well known for its remarkable antibiotic producing ability and the potential capacity to produce salt tolerant extracellular enzyme such as amylase, nuclease and proteinase. The betaine produced by salt tolerant actinobacteria is efficient preservative and stabilizer, which has potential application in the fields of medical industry, biological chemistry and environmental protection. Studies on the actinobacterial diversity in salt environment would promote the development and utilization of actinomycetes resources. This study aims at investigating the diversity of actinobacteria in Aiding Lake, a hypersaline lake and the lowest land point in China. The diversity of actinobacteria in the sediment from Aiding Lake was investigated by culture-independent method based on phylogenetic analysis of 16S rDNA gene sequences and selective isolation method.Specific primers were used to amplify the actinobacterial 16S rDNA gene, and corresponding clone libraries were constructed for the sediment samples. Different clones selected on the basis of HaeIII digestion patterns were sequenced. Nine selective media with different salinities were used to isolate actinobacteria from the sediment samples. The analysis of 16S rDNA gene sequences showed that 273 clone sequences belonged to subclasses Actinobacteridae (208), Acidimicrobidae (13) and Rubrobacteridae (52), respectively. 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 novel taxa. Some sequences, which formed several distinct clades in phylogenetic tree may represent novel taxonomical groups of Actinobacteria.55 strains were isolated by different selective media. They were belonged to 6 suborders of the order Actinomycetales, of which Streptomyces and Nocardiopsis were the dominant groups. Some rare actinomycetes were isolated, in genus of Actinopolyspora, Amycolatopsis, Verrucosispora, Saccharopolyspora, Micrococcus and Saccharomonospora. 3 potential novel species were obtained.Aiding lake harbors abundant actinobacteria, including large number of unknown actinobacterial groups, is worth while for further study.