Bacterial community in saline farmland soil on the Tibetan plateau: responding to salinization while resisting extreme environments

Abstract

Background Salinization damages the health of soil systems and reduces crop yields. Responses of microbial communities to salinized soils and their functional maintenance under high salt stress are valuable scientific problems. Meanwhile, the microbial community of the salinized soil in the plateau environment is less understood. Here, we applied metagenomics technology to reveal the structure and function of microorganisms in salinized soil of the Tibetan Plateau. Results The diversity of composition and function of microbial community in saline soil have changed significantly. The abundances of chemoautotrophic and acidophilic bacteria comprising Rhodanobacter, Acidobacterium, Candidatus Nitrosotalea, and Candidatus Koribacter were significantly higher 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 than the non-saline soil. Both types of soils were rich in genes encoding resistance to environmental stresses (i.e., cold, ultraviolet light, and hypoxia in Tibetan Plateau). The resistance of the soil microbial communities to the saline environment is based on the absorption of K+ as the main mechanism, with cross-protection proteins and absorption buffer molecules as auxiliary mechanisms in our study area. 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 responses to soil salinization and the potential ecological risks in the special plateau environment.

Salinity of irrigation water selects distinct bacterial communities associated with date palm (Phoenix dactylifera L.) root

“…Our results are in agreement with the previous studies, reporting irrigation source specific distinct bacterial communities in plants (i.e. cotton and barley) grown in arid environment 6 , 17 , 18 . The observed community structural pattern can be explained by a deterministic salinity filtering process, wherein the selection of bacterial assemblages depend on the salinity tolerance of date palm roots.…”

“…Soil EC and irrigation water pH were the most important factors affecting root-associated bacterial community structural patterns. Firstly, salinity (which is an indirect measure of soil EC) is one of the key determinants for soil microbial communities in a desert ecosystem 35 and it is known to affect desert plant root-associated bacterial communities 18 , 35 . The soil EC mediated alteration in bacterial taxa can potentially influence nutrient availability since salinity and nitrogen concentrations are reportedly inter-connected in the rhizosphere 36 .…”

“…We also expect similar structuring of bacterial communities in date palm roots under non-saline freshwater and saline groundwater irrigation. At compositional level, saline groundwater enrich Gemmatimonadetes and Actinobacteria phyla in cotton field soil 6 , 17 , while barley field soil enrich specific genera namely Rhodanobacter , Candidatus Koribacter and Burkholderia 18 . Previous studies in date palm show compartment-specific selection of taxa 15 , 19 , wherein Gammaproteobacteria was dominant 19 , while another study show enrichment of Pseudomonas and Rahnella genera 20 in the roots.…”

Irrigation water salinity structures the bacterial communities of date palm (Phoenix dactylifera)-associated bulk soil

“…Soil salinity is an important determinant of bacterial richness ( Zhang et al, 2019 ; Li et al, 2021b ) and Shannon diversity index ( Guo et al, 2021 ; Yu et al, 2021 ; Nan et al, 2022 ) in arid ecosystems. Apart from soil salinity, irrigation water salinity also affect the Shannon diversity index, both negatively ( Zheng et al, 2017 ; Chen et al, 2019 ; Hou et al, 2021 ) and positively ( Chen et al, 2017 ) in arid soil.…”

“…Another study in which saline groundwater with different saline ranges was used for irrigating cotton field soil, showed an increase in Proteobacteria and Actinobacteriota and a decrease in Planctomycetes and Bacteroidetes ( Chen et al, 2017 ). Soil salinity is shown to increase the abundance of Halobacteria and Nitriliruptoria genera in maize ( Li et al, 2021a ) and Rhodanobacter, Acidobacterium, Candidatus Nitrosotalea, and Candidatus Koribacter in barley field soil ( Li et al, 2021b ). These bacterial taxa present in arid soils of agroecosystems possibly withstand salinity stress by producing spores, extracellular polysaccharides (EPS), antioxidant enzymes, and osmolytes that possibly confer salinity tolerance in arid soil ( Alsharif et al, 2020 ).…”