Composition and functional diversity of extreme halophiles isolated from two salt lakes in Xinjiang

Abstract:

[Objective] To investigate the functional characteristics of cultivable extreme halophiles by analyzing the differences of community composition of extreme halophiles in salt lakes with different types of salt formation. [Methods] Soil samples were collected from Qijiaojing Salt Lake (sulfate type) and Nanhu Salt Lake (carbonate type) in Xinjiang, and extreme halophiles were isolated by the dilution plating method. By morphological observation and characteristic analysis, the representative strains were screened. The salt-tolerance of the strains was tested and the 16S rRNA gene sequencing was performed. Functional activities of the extreme halophiles were also detected, including protease, amylase, cellulase and lipase activities as well as phenol degradation ability. [Results] A total of 1 679 strains of extreme halophiles were obtained, and 45 representative strains were screened, which belonged to 5 phyla and 14 genera, and the number of archaea (accounting for 70.58%) was significantly more than that of bacteria. The optimal salt concentration for growth was in the range of 18.4%–20.0%. At the genus level, the dominant groups were Haloterrigena (32.94%) and Natrialba (26.03%) in archaea, and Aquisalimonas (9.85%) and Aliifodinibius (8.10%) in bacteria. In the two salt lakes, the species richness of Nanhu Salt Lake with lower salinity was higher than that of Qijiaojing Salt Lake, but the composition of archaea species was similar, mainly Haloterrigena. There were differences in bacterial community composition; specifically, Aquisalimonas was dominant in Nanhu Salt Lake, while Aliifodinibius was dominant in Qijiaojing Salt Lake. Functional diversity screening showed that the total positive rate was 80%, and 42.58% of the strains produced amylase and were classified into Natrialba. Extreme halophiles producing protease, cellulase and lipase accounted for 9.71%, 9.29% and 7.21%, respectively, and phenol degrading strains occupied 11.14%. [Conclusion] This study revealed the diversity of cultivable extreme halophiles in Xinjiang salt lakes. Archaea was the dominant group and there were also diverse bacterial species, displaying significant activity of various functional enzymes. Additionally, the dominant Natrialba, Haloterrigena, Aquisalimonas and Aliifodinibius had great application potential, which could enrich bacterial resources for future research and application, and were worthy mining.