Diazotrophic community difference between specialists and generalists in response to arsenic and antimony...

Diazotrophs are pivotal in bioremediation, particularly in environments contaminated by metal(loid)s. Despite their significance, the specific impacts of such contamination on the diverse functional groups of soil diazotrophs, including both generalists and specialists, are not well understood. Our study examines the influences of antimony and arsenic contamination on the ecological functions of these diazotrophic groups in areas with high (HC) and low (LC) contamination. Utilizing geochemical analyses, nitrogenase gene (nifH) sequencing, and robust statistical approaches, we assessed the composition and distribution patterns of diazotrophs across different contamination levels. Our results show consistent alpha diversity among diazotrophic subcommunities in both HC and LC sites, highlighting their resilience to metal-induced stress. Generalists exhibited significant compositional shifts between HC and LC sites, whereas specialists remained stable. Network analyses revealed that specialists more frequently occupy central roles than generalists, yet metal stress displaces both groups from these positions within the networks. Deterministic processes were identified as the dominant factors influencing community assembly for both subcommunities. While MST values suggested a similar balance of deterministic and stochastic processes between HC and LC sites, the findings indicate that metal(loid) contamination may still contribute to ecological selection, particularly through Sb and As influencing generalist and specialist composition. These results provide valuable insights into the differential responses of generalist and specialist subcommunities to metal contamination, informing improved ecosystem management and bioremediation strategies.