A comparison of microbial diversity, distribution patterns, and halogenated aromatics biodegrading genes in sediments of two urban rivers

Urban river sediments often serve as reservoirs of halogenated aromatic pollutants, such as polychlorinated biphenyls (PCBs), leading to significantly alterations in the biological characteristics of this ecosystem. Various microbes can degrade halogenated aromatics, serving as a crucial detoxification mechanism that converts toxic pollutants into common metabolites to complete the carbon cycle. However, the impact of PCBs on the diversity and structure of microbial communities in urban rivers has remained largely unexplored. Understanding the dynamics of microbial community structure and function is essential for unraveling biodegradation pathways and interactions of these microbial degraders in PCB-contaminated urban river sediments. In this study, a thorough analysis of microbial diversity and distribution patterns was conducted using 16S rRNA gene-based sequencing in the sediments of two urban rivers, the Dasha River and Maozhou River. Our results unveiled distinct community variances between the two rivers, primarily influenced by environmental factors. The detailed composition and abundance of halogenated aromatic biodegradation related genes were elucidated using metagenomics, mainly contributed by Proteobacteria, Desulfobacterota, and Chloroflexi. Network analysis revealed close interactions among these microbes within each river, indicating a cooperative propensity for PCBs biodegradation, which underscores the interactions as the mode of metabolism and common survival strategy in contaminated rivers.