Integrated Analysis of Soil Metagenome and Soil Metabolome Reveals the Differential Responses of Sorghum and Peanut Rhizosphere Microbes to Salt Stress

Soil salinization is a major constraint to crop cultivation. To improve the use-efficiency of salinized soil, sorghum and peanut are generally considered to be suitable crops for cultivation in these marginal soils. Herein, an artificially simulated salt-stress pot experiment was performed to investigate the effects of salt stress on microbial composition and metabolic profile in rhizosphere soil of sorghum and peanut, respectively. As a consequence, salt stress increased specific metabolites and recruitment of key microbial taxa in sorghum and peanut rhizosphere soils. Sorghum recruits key microbial taxa (including Nocardioides, Massilia, Gemmatirosa, and Pseudolabrys); it also regulates microbial genes encoding enzymes relevant to S_TMSMW0211 (n-Hexadecanoic, Acid) to participate in the fatty acid elongation pathway for salt stress response. The key microbial taxa (including Sphingomonas, and Gemmatimonadetes bacterium) recruited by peanut primarily mediate starch and sucrose metabolism pathway by enabling carbohydrate-related enzymes to cope with salt stress. Generally, the recruited microbial taxa and specific metabolites produced by sorghum and peanut under salt stress are associated with energy metabolism. This indicates that microbes potentially help their host cope with salt stress by mediating energy supply. This study revealed different strategies for salt stress response between the two crops at the microbiological level. The findings may help in identifying beneficial microbes that help plants cope with salt stress. Our findings can also provide novel perspectives for optimizing saline soil cultivation from the microbial management perspective.