title: Toxicity of perfluorooctane sulfonate and perfluorooctanoic acid to Escherichia coli: Membrane disruption, oxidative stress, and DNA damage induced cell inactivation and/or death.
abstract: Perfluorooctane sulfonate (PFOS) and perfluorooctanoic acid (PFOA) are two widely used polyfluorinated compounds (PFCs) and are persistent in the environment. This study for the first time systematically investigated their toxicities and the underlying mechanisms to Escherichia coli. Much higher toxicity was observed for PFOA than PFOS, with the 3 h half growth inhibition concentrations (IC50) determined to be 10.6 ± 1.0 and 374 ± 3 mg L(-1), respectively, while the bacterial accumulation of PFOS was much greater than that of PFOA. The PFC exposures disrupted cell membranes as evidenced by the dose-dependent variations of cell structures (by transmission electron microscopy observations), surface properties (electronegativity, hydrophobicity, and membrane fluidity), and membrane compositions (by gas chromatogram and Fourier transform infrared spectroscopy analyses). The increases in the contents of intracellular reactive oxygen species (ROS) and malondialdehyde and the activity of superoxide dismutase indicated the increment of oxidative stress induced by the PFCs in the bacterial cells. The fact that the cell growth inhibition was mitigated by the addition of ROS scavenger (N-acetyl cysteine) further evidenced the important role of oxidative damage in the toxicities of PFOS and PFOA. Eighteen genes involved in cell division, membrane instability, oxidative stress, and DNA damage of the exposed cells were up or down expressed, indicating the DNA damage by the PFCs. The toxicities of PFOS and PFOA to E. coli were therefore ascribed to the membrane disruption, oxidative stress, and DNA damage induced cell inactivation and/or death. The difference in the bactericidal effect between PFOS and PFOA was supposed to be related to their different dominating toxicity mechanisms, i.e., membrane disruption and oxidative damage, respectively. The outcomes will shed new light on the assessment of ecological effects of PFCs.
authors.affiliation: Department of Environmental Science, Zhejiang University, Hangzhou 310058, China.
authors.forename: Gesheng
authors.initials: G
authors.lastname: Liu
authors.affiliation: Department of Environmental Science, Zhejiang University, Hangzhou 310058, China.
authors.forename: Shuai
authors.initials: S
authors.lastname: Zhang
authors.affiliation: Department of Environmental Science, Zhejiang University, Hangzhou 310058, China; Zhejiang Provincial Key Laboratory of Organic Pollution Process and Control, Zhejiang University, Hangzhou 310058, China.
authors.forename: Kun
authors.initials: K
authors.lastname: Yang
authors.affiliation: Department of Environmental Science, Zhejiang University, Hangzhou 310058, China; Zhejiang Provincial Key Laboratory of Organic Pollution Process and Control, Zhejiang University, Hangzhou 310058, China.
authors.forename: Lizhong
authors.initials: L
authors.lastname: Zhu
authors.affiliation: Department of Environmental Science, Zhejiang University, Hangzhou 310058, China; Zhejiang Provincial Key Laboratory of Organic Pollution Process and Control, Zhejiang University, Hangzhou 310058, China. Electronic address: lindaohui@zju.edu.cn.
authors.forename: Daohui
authors.initials: D
authors.lastname: Lin
mesh_terms: D017738:Alkanesulfonic Acids / Q000633:toxicity*; D002210:Caprylates / Q000633:toxicity*; D002462:Cell Membrane / Q000187:drug effects* / Q000235:genetics / Q000378:metabolism / Q000648:ultrastructure; D004249:DNA Damage; D004305:Dose-Response Relationship, Drug; D004785:Environmental Pollutants / Q000633:toxicity*; D048168:Escherichia coli K12 / Q000187:drug effects* / Q000235:genetics / Q000378:metabolism; D005466:Fluorocarbons / Q000633:toxicity*; D015870:Gene Expression / Q000187:drug effects; D008560:Membrane Fluidity / Q000187:drug effects; D050296:Microbial Viability / Q000187:drug effects / Q000235:genetics; D046529:Microscopy, Electron, Transmission; D018384:Oxidative Stress / Q000187:drug effects*; D017382:Reactive Oxygen Species / Q000378:metabolism; D017550:Spectroscopy, Fourier Transform Infrared; D013482:Superoxide Dismutase / Q000378:metabolism; D013499:Surface Properties
chemical_list: D017738:Alkanesulfonic Acids; D002210:Caprylates; D004785:Environmental Pollutants; D005466:Fluorocarbons; D017382:Reactive Oxygen Species; C023036:perfluorooctanoic acid; C076994:perfluorooctane sulfonic acid; D013482:Superoxide Dismutase
keywords: Bacterium; Bioaccumulation; Growth inhibition; Polyfluorinated compounds; Toxicity mechanism