Degradation and deactivation of a plasmid-encoded extracellular antibiotic resistance gene during separate and combined exposures to UV254 and radicals

WATER RESEARCH

卷:182

Article

Nihemaiti, Maolida¹  Yoon, Younggun²  He, Huan³  Dodd, Michael C.³  Croue, Jean-Philippe^1,4  Lee, Yunho² 

[1] Curtin Univ, Dept Chem, Curtin Water Qual Res Ctr, GPO Box U1987, Perth, WA 6845, Australia

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

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

[4] Univ Poitiers, Inst Chim Milieux & Mat IC2MP, CNRS, UMR 7285, Poitiers, France

关键词: Antibiotic resistant bacteria;    Antibiotic resistance genes;    Gene transformation;    UV;    Hydroxyl radical;    Sulfate radical;   

DOI  :  10.1016/j.watres.2020.115921

来源: Elsevier

【 摘 要 】

This study investigated the degradation and deactivation of an extracellular ampicillin resistance gene (amp(R)) encoded in plasmid pUC19 during exposure to UV254, (OH)-O-center dot (generated by UV>290/H2O2), and combined exposure to UV254 and (OH)-O-center dot (and/or SO4 center dot-) using UV254/H2O2 and UV254/S2O82-. The degradation rates of amp(R) measured by quantitative polymerase chain reaction increased with increasing target amplicon length (192-851 bps). The rate constants for the degradation of pUC19 (2686 bps) were calculated as 0.26 cm(2)/mJ for UV254 and 1.5 x 10(11) M(-1)s(-1) for (OH)-O-center dot, based on the degradation rates of amp(R) amplicons and assuming an equal sensitivity of DNA damage across the entire plasmid. DNA repair-proficient Escherichia coli (E. coli) AB1157 strain (wild-type) and its repair-deficient mutants including AB1886 (uvrA(-)), AB2463 (recA(-)), AB2480 (uvrA(-), recA(-)), and DH5 alpha (recA(-), endA(-)) were applied as recipient cells in gene transformation assays. Results suggested that the elimination efficiency of transforming activity during UV254 and( center dot)OH exposure was dependent on the type of DNA repair genes in recipient E. coli strains. Losses of transforming activity were slower than the degradation of pUC19 by a factor of up to similar to 5 (for E. coli DH5 alpha), highlighting the importance of DNA repair in recipient cells. The degradation rates of ampR amplicons were much larger (by a factor of similar to 4) in UV254/H2O2 and UV254/S2O82- than UV254 direct photolysis, indicating the significant contribution of (OH)-O-center dot and SO4 center dot- to the gene degradation. Not only UV254 and SO4 center dot-, but also (OH)-O-center dot contributed to the degradation of ampR during UV254/S2O82-, which was attributed to the conversion of SO4 center dot- to (OH)-O-center dot and a 10-fold larger reactivity of (OH)-O-center dot towards amp(R) as compared to SO4 center dot-. However, the enhanced gene degradation by radicals did not lead to a faster elimination of gene transforming activity during UV254/H2O2 and UV254/S2O82-, suggesting that UV254- and radical-induced DNA damage were not additive in their contributions to losses of gene transforming activity. Wastewater effluent organic matter (EfOM) accelerated the degradation of ampR during UV254 irradiation by means of reactive species production through indirect photolysis reactions, whereas EfOM mainly acted as a radical scavenger during UV254/H2O2 and UV254/S2O82- treatments. (C) 2020 Elsevier Ltd. All rights reserved.

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