Revealing the critical role of rare bacterial communities in shaping antibiotic resistance genes in saline soils through metagenomic analysis

Abstract

Salinity is considered one of the basic abiotic factors influencing the diversity and distribution of antibiotic resistance genes (ARGs) in soils, yet little is known about the distribution and driving factors of ARGs in naturally saline soils. In this study, metagenomic analysis was conducted to explore the intricate dynamics among soil salinity, microbial community structure and ARGs propagation, with a particular focus on the key contribution of rare potential-hosts of ARGs in light and heavy saline soils. The findings revealed that salinity was significantly negatively correlated with the abundance of ARGs, light saline soils hosted a greater abundance of ARGs than high saline soils, with particularly significant enrichment in genes conferring resistance to multidrug, vancomycin, bacitracin and tetracenomycin C. Proteobacteria and Actinobacteria were identified as primary hosts for ARGs. Notably, rare potential hosts of ARGs play a crucial role in shaping the abundance of ARGs despite their low relative abundance (0.85 %), significantly influencing the relative abundance of ARGs in light and heavy saline soils. The average degree of rare potential-hosts of ARGs was found to be higher in light saline soils (average degree = 45.729 and 25.923 in light and heavy saline soils, respectively), and there was stronger interaction connected between microorganisms (edges = 35,760 and 20,259 in light and heavy saline soils, respectively). Also, microbial community niche width and niche overlap of rare potential-hosts of ARGs in light saline soils were significantly greater than that in heavy saline soils. This work emphasizes the importance of bacterial communities of rare potential-hosts of ARGs on antibiotic resistome, and provides advanced insights into the fate and dissemination of ARGs in saline soils.