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Article Dans Une Revue Water Research Année : 2020

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

Résumé

This study investigated the degradation and deactivation of an extracellular ampicillin resistance gene (ampR) encoded in plasmid pUC19 during exposure to UV254, OH (generated by UV>290/H2O2), and combined exposure to UV254 and OH (and/or SO4•−) using UV254/H2O2 and UV254/S2O82−. The degradation rates of ampR 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 cm2/mJ for UV254 and 1.5 × 1011 M−1s−1 for OH, based on the degradation rates of ampR 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 DH5α (recA, endA) were applied as recipient cells in gene transformation assays. Results suggested that the elimination efficiency of transforming activity during UV254 and 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 ∼5 (for E. coli DH5α), highlighting the importance of DNA repair in recipient cells. The degradation rates of ampR amplicons were much larger (by a factor of ∼4) in UV254/H2O2 and UV254/S2O82− than UV254 direct photolysis, indicating the significant contribution of OH and SO4•− to the gene degradation. Not only UV254 and SO4•−, but also OH contributed to the degradation of ampR during UV254/S2O82−, which was attributed to the conversion of SO4•− to OH and a 10-fold larger reactivity of OH towards ampR as compared to SO4•−. 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.
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Dates et versions

hal-03492495 , version 1 (15-07-2022)

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Paternité - Pas d'utilisation commerciale

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Maolida Nihemaiti, Younggun Yoon, Huan He, Michael C. Dodd, Jean-Philippe Croué, et al.. Degradation and deactivation of a plasmid-encoded extracellular antibiotic resistance gene during separate and combined exposures to UV254 and radicals. Water Research, 2020, 182, pp.115921 -. ⟨10.1016/j.watres.2020.115921⟩. ⟨hal-03492495⟩
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