The secondary metabolite hydrogen cyanide protects Pseudomonas aeruginosa against sodium hypochlorite-induced oxidative stress

Waleska Stephanie da Cruz Nizer; Madison Elisabeth Adams; Vasily Inkovskiy; Carole Beaulieu; Joerg Overhage

doi:10.3389/fmicb.2023.1294518

The secondary metabolite hydrogen cyanide protects Pseudomonas aeruginosa against sodium hypochlorite-induced oxidative stress

Front Microbiol. 2023 Nov 16:14:1294518. doi: 10.3389/fmicb.2023.1294518. eCollection 2023.

Authors

Waleska Stephanie da Cruz Nizer¹, Madison Elisabeth Adams¹, Vasily Inkovskiy¹, Carole Beaulieu¹, Joerg Overhage¹

Affiliation

¹ Department of Health Sciences, Carleton University, Ottawa, ON, Canada.

Abstract

The high pathogenicity of Pseudomonas aeruginosa is attributed to the production of many virulence factors and its resistance to several antimicrobials. Among them, sodium hypochlorite (NaOCl) is a widely used disinfectant due to its strong antimicrobial effect. However, bacteria develop many mechanisms to survive the damage caused by this agent. Therefore, this study aimed to identify novel mechanisms employed by P. aeruginosa to resist oxidative stress induced by the strong oxidizing agent NaOCl. We analyzed the growth of the P. aeruginosa mutants ΔkatA, ΔkatE, ΔahpC, ΔahpF, ΔmsrA at 1 μg/mL NaOCl, and showed that these known H₂O₂ resistance mechanisms are also important for the survival of P. aeruginosa under NaOCl stress. We then conducted a screening of the P. aeruginosa PA14 transposon insertion mutant library and identified 48 mutants with increased susceptibility toward NaOCl. Among them were 10 mutants with a disrupted nrdJa, bvlR, hcnA, orn, sucC, cysZ, nuoJ, PA4166, opmQ, or thiC gene, which also exhibited a significant growth defect in the presence of NaOCl. We focussed our follow-up experiments (i.e., growth analyzes and kill-kinetics) on mutants with defect in the synthesis of the secondary metabolite hydrogen cyanide (HCN). We showed that HCN produced by P. aeruginosa contributes to its resistance toward NaOCl as it acts as a scavenger molecule, quenching the toxic effects of NaOCl.

Keywords: Pseudomonas aeruginosa; antimicrobial resistance; hydrogen cyanide; oxidative stress; oxidative stress response; reactive chlorine species; sodium hypochlorite.

Grants and funding

The author(s) declare financial support was received for the research, authorship, and/or publication of this article. This research was funded by Carleton University and the Natural Sciences and Engineering Research Council of Canada (NSERC, RGPIN-2019-06335).