Sublethal Paraquat Confers Multidrug Tolerance in Pseudomonas aeruginosa by Inducing Superoxide Dismutase Activity and Lowering Envelope Permeability

Abstract

Stressors and environmental cues shape the physiological state of bacteria, and thus how they subsequently respond to antibiotic toxicity. To understand how superoxide stress can modulate survival to bactericidal antibiotics, we examined the effect of intracellular superoxide generators, paraquat and menadione, on stationary-phase antibiotic tolerance of the opportunistic pathogen, Pseudomonas aeruginosa. We tested how pre-challenge with sublethal paraquat and menadione alters the tolerance to ofloxacin and meropenem in wild-type P. aeruginosa and mutants lacking superoxide dismutase (SOD) activity (sodAB), the paraquat responsive regulator soxR, (p)ppGpp signaling (relA spoT mutant), or the alternative sigma factor rpoS. We confirmed that loss of SOD activity impairs ofloxacin and meropenem tolerance in stationary phase cells, and found that sublethal superoxide generators induce drug tolerance by stimulating SOD activity. This response is rapid, requires de novo protein synthesis, and is RpoS-dependent but does not require (p)ppGpp signaling nor SoxR. We further showed that pre-challenge with sublethal paraquat induces a SOD-dependent reduction in cell-envelope permeability and ofloxacin penetration. Our results highlight a novel mechanism of hormetic protection by superoxide generators, which may have important implications for stress-induced antibiotic tolerance in P. aeruginosa cells.

Vibrio splendidus persister cells induced by host coelomic fluids show a similar phenotype to antibiotic‐induced counterparts

“…Whether the coelomic fluids-induced and antibioticresistant cells are bona fide persister cells is an important question in our study. In our experiments, we used several experimental methods to characterize persister cells (Kim et al, 2018), which have also been validated by 15 independent labs to date (Johnson and Levin, 2013;Kwan et al, 2013;Grassi et al, 2017;Cui et al, 2018;Jin et al, 2018;Narayanaswamy et al, 2018;Sulaiman et al, 2018;Tkhilaishvili et al, 2018;Pu et al, 2019;Martins et al, 2020;Rowe et al, 2020;Sun et al, 2020;Yu et al, 2020;Zhao et al, 2020;Zheng et al, 2020). These methods are mainly based on the phenotypes of low metabolic activity, high gene expression of ppGpp-pathway related genes, invariable MIC, multidrug tolerance, pathogenicity of re-grown persister cells, and high phenotype heterogeneity.…”

Susceptibility to Antibiotics and Reactive Oxygen Species in Escherichia coli: A Survey of Clinical and Environmental Isolates

“…The linkage between resistance towards superoxide-generating agents, such as PQ, and diminished susceptibility to several antibiotics, have been shown in laboratory conditions, in E. coli and other gram-negative bacteria (e.g., [17]). However, such a linkage was not found, and perhaps even just the opposite.…”

Non-Canonical Aspects of Antibiotics and Antibiotic Resistance

“…Cu and Zn increase conjugation [129] (or inhibit conjugation by reducing the expression of conjugative genes [130]); Cu facilitates conjugative transfer of ICEs across bacterial genera [131]. Paraquat confers tolerance in P. aeruginosa by inducing SOS and diminishing membrane permeability [132]; it induces soxRS in E. coli, decreasing antibiotic effects [89]. Chloroxylenol promotes conjugation [133].…”