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ORIGINAL RESEARCH article

Front. Microbiol.

Sec. Aquatic Microbiology

Volume 16 - 2025 | doi: 10.3389/fmicb.2025.1593147

This article is part of the Research TopicMitigating Microbial Contamination of Drinking Water SourcesView all 5 articles

Varying effects of chlorination on microbial functional repertoire and gene expression in contrasting effluents

Provisionally accepted
  • Hong Kong University of Science and Technology, Kowloon, Hong Kong, SAR China

The final, formatted version of the article will be published soon.

Effluents produced from different influent sources and sewage treatment processes carry distinct microbial community compositions. These microbiomes exhibit varying degrees of resistance and resilience under chlorination; however, their survival strategies and potential risks to the public health and ecosystem have yet to be fully characterized. In view of this, we subjected microbiomes from two contrasting types of effluents with distinct influent properties (seawater/freshwater-based) and prior treatment processes (primary/secondary) to metagenomics and metatranscriptomics analyses for comparing the alterations in their functional genes and activities under chlorination. The effluents presented highly dissimilar genomic and transcriptomic profiles. The variations in these profiles were significantly correlated to physicochemical factors including salinity, DO, BODâ‚…, TSS and TN. We recovered novel metagenome-assembled genomes (MAGs) from each type of effluent, revealing that those recovered from the same effluent tended to share similar functional properties which aligned with the physicochemical parameters of the effluent. Notably, the type and extent of alterations in genomic and transcriptomic profiles under chlorination varied greatly between effluents. Most of the genes and transcripts with significant changes in relative abundances were exclusive to their respective effluents. Also, the number of genes and transcripts with significant increase in relative abundances after chlorination were much higher than those with reduction. These enriched genes and transcripts were responsible for a wide range of functions, including energy generation, repair of damaged components and stress responses. Furthermore, the remanent microbiomes in chlorinated effluents still harbored numerous genes related to waterborne diseases and antimicrobial resistance, suggesting the potential risks of discharging these effluents into the environment. This study revealed the diverse effects of chlorination on different types of effluent microbiomes. It suggested that the remanent microbiomes in chlorinated effluents would have great variance in genetic potential and activities, providing insights into the evaluation and regulation of chlorine disinfection in sewage treatment.

Keywords: Metagenomics, metatranscriptomics, sewage effluents, chlorination, microbiomes, functional genes, Gene Expression

Received: 13 Mar 2025; Accepted: 03 Jun 2025.

Copyright: © 2025 Tang and Lau. This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY). The use, distribution or reproduction in other forums is permitted, provided the original author(s) or licensor are credited and that the original publication in this journal is cited, in accordance with accepted academic practice. No use, distribution or reproduction is permitted which does not comply with these terms.

* Correspondence: Stanley Chun Kwan Lau, Hong Kong University of Science and Technology, Kowloon, Hong Kong, SAR China

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