Diversity of culturable bacteria and their extracellular active substance properties in alpine lakes of Southwest China

Abstract:

[Objective] The main aim of this study is to study the diversity of culturable bacteria in alpine lakes of different regions located in Southwest China, and to analyze their capabilities for producing proteases, cellulases and exopolysaccharides. [Methods] Four water samples in different alpine lakes located in Southwest China, including Horse Lake in Leibo (LB), Kanbon sub Lake in Sino-Burmese border (ZM), Lotus Lake in Shade (SD) and Qinghai Lake in Tengchong (TC), were collected to isolate the cultural bacteria based on the spread plate method. The genera of culturable bacteria were identified by analyzing the physiological and biochemical indexes and 16S rRNA gene sequences. The strains were further detected for production of proteases, cellulases and exopolysaccharides. [Results] A total of 41 strains were isolated from four lakes in southwestern China, of which 15 strains from LB, 13 strains ZM, 7 strains SD and 6 strains TC. According to phylogenetic analysis of 16S rRNA gene sequences, there were obvious differences in composition and abundance of culturable bacteria among four lakes. The dominant genus was Bacillus, and followed by Aeromonas and Pseudomonas in LB and ZM. All isolates were Bacillus in TC, whereas strains were highly specific in SD. Further research on enzyme activities and exopolysaccharides were detected in 41 cultural bacteria, of which 28 strains had protease activity, 6 strains had cellulase activity and 17 strains produced exopolysaccharides (EPS). In addition, 2 strains produced proteases, cellulases and exopolysaccharides simultaneously, 10 strains produced proteases and exopolysaccharides, 2 strains produced proteases and cellulases, and only 1 strain produced cellulases and exopolysaccharides. [Conclusion] The culturable bacteria in alpine lakes were capable of secreting various extracellular active substances, with potential for further development and research.