Transient Oxygen Exposure Causes Profound and Lasting Changes to a Benzene-Degrading Methanogenic Community.

Environ Sci Technol

Department of Chemical Engineering and Applied Chemistry, University of Toronto, 200 College Street, Toronto, Ontario M5S 3E5, Canada.

Published: September 2022

We investigated the impact of oxygen on a strictly anaerobic, methanogenic benzene-degrading enrichment culture derived decades ago from oil-contaminated sediment. The culture includes a benzene fermenter from candidate clade Sva0485 (referred to as ORM2) and methanogenic archaea. A one-time injection of 0.1 mL air , simulating a small leak into 30 mL batch culture bottle, had no measurable impact on benzene degradation rates, although retrospectively, a tiny enrichment of aerobic taxa was detected. A subsequent 100 times larger injection of air stalled methanogenesis and caused drastic perturbation of the microbial community. A benzene-degrading became highly enriched and consumed all available oxygen. Anaerobic benzene-degrading ORM2 cell numbers plummeted during this time; re-growth and associated recovery of methanogenic benzene degradation took almost 1 year. These results highlight the oxygen sensitivity of this methanogenic culture and confirm that the mechanism for anaerobic biotransformation of benzene is independent of oxygen, fundamentally different from established aerobic pathways, and is carried out by distinct microbial communities. The study also highlights the importance of including microbial decay in characterizing and modeling mixed microbial communities.

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http://www.ncbi.nlm.nih.gov/pmc/articles/PMC9496526PMC
http://dx.doi.org/10.1021/acs.est.2c02624DOI Listing

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