Degradation and deactivation of plasmid-encoded antibiotic resistance genes during exposure to ozone and chlorine

WATER RESEARCH

卷:202

Article

Yoon, Younggun¹  He, Huan²  Dodd, Michael C.²  Lee, Yunho¹ 

[1] Gwangju Inst Sci & Technol GIST, Sch Earth Sci & Environm Engn, Gwangju 61005, South Korea

[2] Univ Washington, Dept Civil & Environm Engn, Seattle, WA 98195 USA

关键词: Antibiotic resistance genes;    Gene transformation;    Ozone;    Chlorine;    Radicals;    DNA repair;   

DOI  :  10.1016/j.watres.2021.117408

来源: Elsevier

【 摘 要 】

Degradation and deactivation kinetics of an antibiotic resistance gene (ARG) by ozone (O-3) and free available chlorine (FAC) were investigated in phosphate-buffered solutions at pH 7 for O-3 (in the presence of tert-butanol), and pH 6.8 or 8.1 for FAC. We used a plasmid (pUC19)-encoded ampicillin resistance gene (amp(R)) in both extracellular (e-) and intracellular (i-) forms. The second-order rate constant (k(O3)) for degradation of 2686 base pair (bp) long e-pUC19 toward O-3, which was determined by quantitative polymerase chain reaction assay, was calculated to be similar to 2 x 10(5) M(-1)s(-1). The deactivation rate constants of e-pUC19 by O-3 measured with various recipient E. coli strains were within a factor of 2 compared with the degradation rate constant for e-pUC19. The degradation/deactivation kinetics of i-pUC19 were similar to those of e-pUC19, indicating only a minor influence of cellular components on O-3 reactivity toward i-pUC19. For FAC, the degradation and deactivation rates of e-pUC19 were decreased in the presence of tert-butanol, implying involvement of direct FAC as well as some radical (e.g., (OH)-O-center dot) reactions. The degradation rates of e-amp(R) segments by direct FAC reaction could be explained by a previously-reported two-step sequential reaction model, in which the rate constants increased linearly with e-amp(R) segment length. The deactivation rate constants of e-pUC19 during exposure to FAC were variable by a factor of up to 4.3 for the different recipient strains, revealing the role of DNA repair in the observed deactivation efficiencies. The degradation/deactivation of e-pUC19 were significantly faster at pH 6.8 than at pH 8.1 owing to pH-dependent FAC speciation variation, whereas i-pUC19 kinetics exhibited much smaller dependence on pH, demonstrating intracellular plasmid DNA reactions with FAC occurred at cytoplasmic pH (similar to 7.5). Our results are useful for predicting and/or measuring the degradation/deactivation efficiency of plasmid-encoded ARGs by water treatment with ozonation and chlorination.

【 授权许可】

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