Positive contribution of predatory bacterial community to multiple nutrient cycling and microbial network complexity in arsenic-contaminated soils

Predatory bacteria are an essential group of micro-predators that can potentially regulate and control soil microbial communities and functions. Although soil arsenic (As) contamination affects soil microbial communities and ecosystem functions, the responses of predatory bacterial communities to As contamination and their contributions to soil multi-nutrient cycling remain unclear. This research gap hinders our ability to assess the effect of predatory bacteria on ecosystem service provision. Here, we used high-throughput Illumina sequencing of 16S rRNA gene amplicon technology to explore the community characteristics of predatory bacteria under varying levels of As contamination and its relationship to soil multi-nutrient cycling functions and microbial network complexity. We found that microbial network complexity and predatory bacterial diversity were significantly decreased at high As-contaminated sites than at non-contaminated sites (P < 0.05). As contamination also altered the composition of predatory bacteria, reducing the abundance of Anaeromyxobacter and Haliangium. By contrast, As contamination increased the relative abundance of some predatory bacterial genera resistant to heavy metal stress, such as Lysobacter and Ensifer. In As-contaminated soil, predatory bacterial diversity was significantly positively correlated with microbial network complexity and soil multi-nutrient cycling (P < 0.05). The abundance of dominant predatory bacteria was also significantly correlated with the abundance of keystone OTUs in the microbial network and soil multi-nutrient cycling (P < 0.05). Overall, predatory bacterial communities may contribute to the multi-nutrient cycling and microbial network complexity of As-contaminated soil, highlighting the potential role of predatory bacteria in maintaining microbial community stability and promoting soil nutrient cycling.