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Metagenomics and metatranscriptomics reveal pathway of 3-Chloroaniline degradation in wastewater reactors
Reference: bioRxiv: 2021.2005.2002.442374

Biological wastewater treatment systems are often affected by major shifts in influent quality, including the input of various toxic chemicals. Yet the mechanisms underlying adaptation of activated sludge process performance when challenged with a sustained toxin input have not been studied in a controlled and replicated experiment. Three replicate bench-scale bioreactors were subjected to a chemical disturbance in the form of 3-chloroaniline (3-CA) input over 132 days, following an acclimation period of 58 days, while three control reactors received no 3-CA input. The nitrification process was initially affected by 3-CA input; yet all three treatment reactors evolved to biologically degrade 3-CA within three weeks of the experiment, resulting in partial nitrification recovery. 16S rRNA amplicon sequencing revealed that ammonia oxidizers were initially impacted by 3-CA, and a new ammonia oxidizing community emerged with the onset of 3-CA degradation. Combining process and microbial community data from amplicon sequencing with potential functions gleaned from assembled metagenomics and metatranscriptomics data, 3-CA degradation was shown to likely occur via a phenol monooxygenase followed by ortho-cleavage of the aromatic ring. The relative abundance of genera Gemmatimonas, Saprospiraceae OLB8 and Taibaiella correlated significantly with 3-CA degradation. This study demonstrated the impact of a sustained stress on the activated sludge community and wastewater treatment process and its subsequent recovery. Using a combination of techniques in a controlled and replicated experiment, we showed that microbial communities can evolve degradative capacity following a sustained xenobiotic input, specific functions like nitrification can fully or partially recover and targeted culture-independent approaches can be used to elucidate the mechanisms of adaptation.

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Published By
Seshan H., Santillan E., Constancias F., Chandra Segaran U.S., Williams R. B. H., Wuertz S.