BTEX biodegradation is linked to bacterial community assembly patterns in contaminated groundwater ecosystem

The control of degrader populations and the stochasticity and certainty of the microbial community in contaminated groundwater are not well-understood. In this study, a long-term contaminated groundwater ecosystem was selected to investigate the impact of BTEX on microbial communities and how microbial communities respond to BTEX pollution. 16S rRNA gene sequencing and metagenomic sequencing provided insights on microbial community assemblage patterns and their role in BTEX cleaning. The operational taxonomy units (OTUs) in the contaminated groundwater ecosystem were clustered distinguishably between the Plume and the Deeper Zone (lower contaminated zone). βNTI analysis revealed that the assembly strategies of abundant and rare OTU subcommunities preferred deterministic processes. Redundancy Analysis (RDA) and mantel testing indicated that benzene, toluene, ethylbenzene, and xylenes (BTEX) strongly drove the abundant OTU subcommunity, while the rare OTU subcommunity was only weakly affected. Deltaproteobacteria , the most dominant degrading microorganism, contains the complete degradation genes in the plume layer. In summary, our finding revealed that BTEX was the major factor in shaping the microbial community structure, and functional bacteria contribute greatly to water cleaning. Investigating the pattern of microbial community assembly will provide insights into the ecological controls of contaminant degradation in groundwater. • BTEX shifted bacterial community in contaminated groundwater. • BTEX enriched the degrader community in the Plume. • BTEX deterministically drives Abundant microbial community assembly. • There is no clear driver for rare subcommunity assembly. • Toluene degradation genes are mainly found in Deltaproteobacteria, Clostridia, etc.