biostudies-literatureUnknownVincent MSSociété d&apos;Accélération du Transfert de TechnologiesAgence Nationale de la RechercheCentre National de la Recherche ScientifiqueUnder anaerobic conditions, chlorate is reduced to chlorite, a cytotoxic compound that triggers oxidative stress within bacterial cultures. We previously found that BD Bacto Casamino Acids were contaminated with chlorate. In this study, we investigated whether chlorate contamination is detectable in other commercial culture media. We provide evidence that in addition to different batches of BD Bacto Casamino Acids, several commercial agar powders are contaminated with chlorate. A direct consequence of this contamination is that, during anaerobic growth, Escherichia coli cells activate the expression of <i>msrP</i>, a gene encoding periplasmic methionine sulfoxide reductase, which repairs oxidized protein-bound methionine. We further demonstrate that during aerobic growth, progressive oxygeMicrobiology spectrume0499122https://www.ebi.ac.uk/biostudies/studies/S-EPMC10100951biostudies-literatureChlorate Contamination in Commercial Growth Media as a Source of Phenotypic Heterogeneity within Bacterial Populations.PMC10100951ANR-21-CE15-0039 NeutrOX#2023-Maturation/Bachlosens#2021-22-BachlosensVergnes AEzraty BVincent MSfalseChlorate Contamination in Commercial Growth Media as a Source of Phenotypic Heterogeneity within Bacterial Populations.Under anaerobic conditions, chlorate is reduced to chlorite, a cytotoxic compound that triggers oxidative stress within bacterial cultures. We previously found that BD Bacto Casamino Acids were contaminated with chlorate. In this study, we investigated whether chlorate contamination is detectable in other commercial culture media. We provide evidence that in addition to different batches of BD Bacto Casamino Acids, several commercial agar powders are contaminated with chlorate. A direct consequence of this contamination is that, during anaerobic growth, Escherichia coli cells activate the expression of <i>msrP</i>, a gene encoding periplasmic methionine sulfoxide reductase, which repairs oxidized protein-bound methionine. We further demonstrate that during aerobic growth, progressive oxyge2023-01-01T00:00:00Z2023 Feb2025-04-04T07:37:43.271Z2025-02-18T23:40:31.325ZS-EPMC101009513675262210.1128/spectrum.04991-22