The responses and adaptations of microbial communities to salinity in farmland soils: A molecular ecological network analysis

Soil salinity is an increasing problem deteriorating soil fertility in degraded farmland soils. However, the responses and adaptations of microbial communities and interactions to salinity in farmland are not yet fully understood. In this study, we used 16S rRNA Miseq-sequencing technique to investigate the phylogenetic compositions, diversity and structure of soil microbial communities under different salinity conditions. The results indicated that prokaryotic diversity decreased with salinity. The change in prokaryotic community was primarily driven by salinity levels. The relative abundances of Proteobacteria, Bacteroidetes and Firmicutes were higher, and those of Acidobacteria and Thaumarchaeota were lower under high salinity than in medium and low salinity soils. Further, microbial network interactions changed along the salinity gradient revealed by a phylogenetic molecular ecological networks (pMENs) analysis. Salinity enhanced the interactions between microorganisms, evidenced by more links, higher average degree and average clustering coefficients within the pMENs in high salinity soils. Furthermore, we constructed the sub-networks of Flavobacterium and Acidobacteria_Gp4 to explore the changes of interactions among different microbial groups under salinity. We found that salinity shifted the interactions among different microbial taxa, and such changes vary among different microbial populations. This study provides solid evidences that microbial communities adapt to salinity through the adjustments of microbial compositions and interactions.