title: Oxidative stress and metabolic perturbations in Escherichia coli exposed to sublethal levels of 2,4-dichlorophenoxyacetic acid.
abstract: The chlorophenoxy herbicide 2,4-dichlorophenoxyacetic acid (2,4-D) is used extensively worldwide despite its known toxicity and our limited understanding of how it affects non-target organisms. Escherichia coli is a suitable model organism to investigate toxicity and adaptation mechanisms in bacteria exposed to xenobiotic chemicals. We developed a methodical platform that uses atomic force microscopy, metabolomics and biochemical assays to quantify the response of E. coli exposed to sublethal levels of 2,4-D. This herbicide induced a filamentous phenotype in E. coli BL21 and a similar phenotype was observed in a selection of genotypically diverse E. coli strains (A0, A1, B1, and D) isolated from the environment. The filamentous phenotype was observed at concentrations 1000 times below field levels and was reversible upon supplementation with polyamines. Cells treated with 2,4-D had more compliant envelopes, significantly remodeled surfaces that were rougher and altered vital metabolic pathways including oxidative phosphorylation, the ABC transport system, peptidoglycan biosynthesis, amino acid, nucleotide and sugar metabolism. Most of the observed effects could be attributed to oxidative stress, consistent with increases in reactive oxygen species as a function of 2,4-D exposure. This study provides direct evidence that 2,4-D at sublethal levels induces oxidative stress and identifies the associated metabolic changes in E. coli.
authors: Department of Chemistry and Biochemistry, University of Regina, 3737 Wascana Parkway, Regina, SK S4S 0A2, Canada.
authors: Supriya V
authors: SV
authors: Bhat
authors: Department of Biological Sciences, University of Calgary, 2500 University Dr, NW Calgary, AB T2N 1N4, Canada.
authors: Sean C
authors: SC
authors: Booth
authors: Department of Chemistry and Biochemistry, University of Regina, 3737 Wascana Parkway, Regina, SK S4S 0A2, Canada.
authors: Erik A N
authors: EA
authors: Vantomme
authors: Department of Biology, University of Regina, 3737 Wascana Parkway, Regina, SK S4S 0A2, Canada.
authors: Shirin
authors: S
authors: Afroj
authors: Department of Biology, University of Regina, 3737 Wascana Parkway, Regina, SK S4S 0A2, Canada.
authors: Christopher K
authors: CK
authors: Yost
authors: Department of Chemistry and Biochemistry, University of Regina, 3737 Wascana Parkway, Regina, SK S4S 0A2, Canada. Electronic address: tanya.dahms@uregina.ca.
authors: Tanya E S
authors: TE
authors: Dahms
mesh_terms: D015084:2,4-Dichlorophenoxyacetic Acid / Q000633:toxicity*; D050260:Carbohydrate Metabolism; D004926:Escherichia coli / Q000187:drug effects* / Q000502:physiology; D015386:Hazardous Substances / Q000633:toxicity*; D006540:Herbicides / Q000633:toxicity; D053858:Metabolic Networks and Pathways; D018384:Oxidative Stress; D017382:Reactive Oxygen Species
chemical_list: D015386:Hazardous Substances; D006540:Herbicides; D017382:Reactive Oxygen Species; D015084:2,4-Dichlorophenoxyacetic Acid
keywords: 2,4-Dichlorophenoxyacetic acid; Atomic force microscopy; Envelope compliance; Filamentous phenotype; Metabolomics; Oxidative stress