Screening and identification of saline-alkali-resistant microbial strains and research on their functions and growth-promoting properties

Abstract:

[Backgroud] In recent years, with the increasing of land salinization in Gansu province, its impact on agricultural production and ecological environment has become more and more serious. [Objective] In this study, saline-alkali-tolerant strains were isolated and screened from the saline-alkali soils of Lanzhou new district of Lanzhou city and Heihe Ecological Reserve of Zhangye city, Gansu province. Then we identified the isolated strains, and evaluated and analyzed some of their functionality and growth-promoting properties, which provided microbial resources and theoretical basis for improving the saline-alkali land in Gansu province. [Methods] The isolated colonies were cultured in conditioned medium of different salinity and alkali concentrations, and those with high saline-alkali tolerance were screened out. The 16S rRNA gene sequencing was used to identify the types of the selected strains and test their various functional and growth-promoting effects in different media. [Results] Five highly saline-alkali-tolerant strains were obtained, which were Bacillus megaterium, Arthrobacter aurescens, Sinorhizobium fredii, Bacillus licheniformis and Acinetobacter sp.. All five strains had the ability to dissolve phosphorus and secrete indole-3-acetic acid (IAA),A. aurescens and B. licheniformis had the ability to dissolve potassium, and A. aurescens, S. fredii and Acinetobacter sp. showed nitrogen fixation ability. ACC deaminase activities secreted by B. licheniformis, B. megaterium and S. fredii reached 0.272, 0.217, and 0.159 U/mg, respectively, while A. aurescens and Acinetobacter sp. had almost no ACC deaminase activity.[Conclusion] The five saline-alkali-tolerant bacteria had different phosphorus-dissolving, potassium-solving and nitrogen-fixing functions and certain growth-promoting effects. This study provided species resources and theoretical basis for the later application of microorganisms to improvement of saline-alkali land.