Bacterial Community in Saline Farmland Soil on the Tibetan Plateau: Responding to Salinization While Resisting Extreme Environments

Background: Soil salinization caused by irrigation will reduce soil health and crop yields. Soil salinization has become one of the world's soil degradation problems. There are few studies on the response of microbial communities to soil salinization in plateau environments. Here, we applied metagenomics technology to make an exploration on the salinized soil microorganisms of the Tibetan Plateau.Results: The metagenomic data results show that the microbial species diversity and genome diversity of saline soil and non-saline soil have changed significantly. we found that the abundances of chemoautotrophic and acidophilic bacteria comprising Rhodanobacter, Acidobacterium, Candidatus Nitrosotalea, and Candidatus Koribacter were significantly higher in saline soil. and the potential degradation of organic carbon in saline soil. The potential degradation of organic carbon in the saline soil, as well as the production of NO and N2O via denitrification, and the production of sulfate by sulfur oxidation were significantly higher compared with the non-saline soil. Both types of soils were rich in genes encoding resistance to environmental stresses (i.e., cold, ultraviolet light, and hypoxia). The resistance of the soil microbial communities to the saline environment on the Tibetan Plateau is based on the absorption of K+ as the main mechanism, with cross-protection proteins and absorption buffer molecules as auxiliary mechanisms. Network analysis showed that functional group comprising chemoautotrophic and acidophilic bacteria had significant positive correlations with electrical conductivity and total sulfur, and significant negative correlations with the total organic carbon, pH, and available nitrogen. The soil moisture, pH, and electrical conductivity are likely to affect the bacterial carbon, nitrogen, and sulfur cycles.Conclusions: These results indicate that the specific environment of the Tibetan Plateau and salinization jointly shape the structure and function of the soil bacterial community, and that the bacterial communities respond to complex and harsh living conditions. In addition, environmental feedback probably exacerbates greenhouse gas emissions and accelerates the reduction in the soil pH. This study will provide insights into the microbial response to soil salinization and the potential ecological risks for the special plateau environment.