Saline soil improvement promotes the transformation of microbial salt tolerance mechanisms and microbial-plant-animal ecological interactions

The improvement of coastal saline land would alleviate the problem of insufficient arable land and provide new solutions for guaranteeing food security and ecological environment modification. In this study, five typical soil samples were collected from Tongzhou Bay, China. The changes in bacterial, animal and plant community composition before and after improvement were comprehensively investigated by a combination of highthroughput sequencing and macro-barcode sequencing analysis of eDNA. The study aimed (1) to characterize the species composition and diversity of the bacterial communities in saline soils, (2) to elucidate the mechanisms of salt tolerance of the bacterial communities, and (3) to investigate the impacts of the microbial salt tolerance mechanisms on the regional bacteria and fauna. The results showed that over 15 years of improvement, the composition of the bacteria in the saline-alkaline plots evolved significantly, changing from Desulfovibrio (10.60%) and Campylobacter (11.20%), to Acidobacter (12.91%). After the improvement, salt stress on the bacterial phyla gradually decreased. The functional differentiation of the bacterial phyla became more pronounced. As ion concentrations decreased, the main mechanism of salt tolerance of the bacterial bacteria changed from mainly mechanism of inorganic ion accumulation (55.56%), supplemented by flexible halophilic enzymes (31.77%), to mainly mechanism of compatible solute (44.80%). The mechanism of microbial salt tolerance directly affected micro-diversity and indirectly influenced the diversity of environmental species (R = 0.54). The results of this study provide a scientific basis for coastal saline land as a microbiodiversity marker and for the exploration of microbial improvement of saline land.