Deciphering the intricate microbial responses and potential degraders of p-chloro-m-xylenol in marine sediments

The widespread use of p -chloro- m -xylenol (PCMX) as a broad-spectrum antimicrobial agent raises concerns about its ecological risks in ecosystems. While prior studies focused on activated sludge systems, the impacts of PCMX on marine systems remain unknown. Here, we systematically investigated the responses of marine sediment communities to PCMX (0.005–50   mg/L) exposure through integrated enzymatic assays, multi-omics, and enrichment culture approaches. High PCMX exposure (50   mg/L) significantly suppressed dehydrogenase (63.8%) and protease (53.8%) activity, reduced microbial diversity, and inhibited nutrient cycling and ATP production. Meanwhile, antibiotic resistance genes associated with efflux pumps were enriched. Metagenomic analysis revealed upregulated aromatic degradation pathways and stress-response mechanisms (e.g., chemotaxis and biofilm formation) under PCMX stress. A halotolerant marine consortium enriched from high-PCMX sediments demonstrated efficient PCMX degradation (50   mg/L, 72   h) across broad salinity (1.5–5.5% NaCl) and temperature (25–40°C) ranges, with metabolite profiling suggesting ortho -cleavage pathways. This work underscores the need for regulatory measures to mitigate the ecological risks posed by PCMX in marine ecosystems, while simultaneously demonstrating the remediation potential of a halotolerant microbial consortium for remediating contaminated environments. Environmental Implications The ubiquitous discharge of PCMX poses an underregulated yet critical threat to ecosystems. Elevated concentrations of PCMX trigger cascading ecological perturbations, including the suppression of enzymatic activities, reduction in microbial diversity, selective enrichment of antibiotic resistance genes, and disruption of carbon/nitrogen cycling as well as energy production in marine sediment systems. Importantly, the developed microbial consortium demonstrates robust PCMX degradation efficacy across fluctuating conditions, facilitating scalable in situ bioremediation. Collectively, these findings highlight the urgent need for regulations on PCMX discharge, systematic ecotoxicity monitoring, and the advancement of nature-based solutions to enhance coastal ecosystem resilience.