Identification of a Toxin–Antitoxin System That Contributes to Persister Formation by Reducing NAD in Pseudomonas aeruginosa
Jingyi Zhou, Shou‐Yi Li, Haozhou Li, Yongxin Jin, Fang Bai, Zhihui Cheng, Weihui Wu
Abstract
Bacterial persisters are slow-growing or dormant cells that are highly tolerant to bactericidal antibiotics and contribute to recalcitrant and chronic infections. Toxin/antitoxin (TA) systems play important roles in controlling persister formation. Here, we examined the roles of seven predicted type II TA systems in the persister formation of a Pseudomonas aeruginosa wild-type strain PA14. Overexpression of a toxin gene PA14_51010 or deletion of the cognate antitoxin gene PA14_51020 increased the bacterial tolerance to antibiotics. Co-overexpression of PA14_51010 and PA14_51020 or simultaneous deletion of the two genes resulted in a wild-type level survival rate following antibiotic treatment. The two genes were located in the same operon that was repressed by PA14_51020. We further demonstrated the interaction between PA14_51010 and PA14_51020. Sequence analysis revealed that PA14_51010 contained a conserved RES domain. Overexpression of PA14_51010 reduced the intracellular level of nicotinamide adenine dinucleotide (NAD+). Mutation of the RES domain abolished the abilities of PA14_51010 in reducing NAD+ level and promoting persister formation. In addition, overproduction of NAD+ by mutation in an nrtR gene counteracted the effect of PA14_51010 overexpression in promoting persister formation. In combination, our results reveal a novel TA system that contributes to persister formation through reducing the intracellular NAD+ level in P. aeruginosa.