Bacterial antibiotic persistence occurs when bacteria are treated with an antibiotic and the majority of the population rapidly dies off, but a small subpopulation enters into a dormant, persistent state and evades death. Diverse pathways leading to nucleoside triphosphate (NTP) depletion and restricted translation have been implicated in persistence, suggesting alternative redundant routes may exist to initiate persister formation. To investigate the molecular mechanism of one such pathway, functional variants of an essential component of translation (phenylalanyltRNA synthetase [PheRS]) were used to study the effects of quality control on antibiotic persistence. Upon amino acid limitation, elevated PheRS quality control led to significant decreases in aminoacylated tRNAPhe accumulation and increased antibiotic persistence. This increase in antibiotic persistence was most pronounced (65-fold higher) when the relA-encoded tRNA-dependent stringent response was inactivated. The increase in persistence with elevated quality control correlated with ;2-fold increases in the levels of the RNase MazF and the NTPase MazG and a 3-fold reduction in cellular NTP pools. These data reveal a mechanism for persister formation independent of the stringent response where reduced translation capacity, as indicated by reduced levels of aminoacylated tRNA, is accompanied by active reduction of cellular NTP pools which in turn triggers antibiotic persistence.
IMPORTANCE Bacterial antibiotic persistence is a transient physiological state wherein cells become dormant and thereby evade being killed by antibiotics. Once the antibiotic is removed, bacterial persisters are able to resuscitate and repopulate. It is thought that antibiotic bacterial persisters may cause reoccurring infections in the clinical setting. The molecular triggers and pathways that cause bacteria to enter into the persister state are not fully understood. Our results suggest that accumulation of deacylated tRNA is a trigger for antibiotic persistence independent of the RelA-dependent stringent response, a pathway thought to be required for persistence in many organisms. Overall, this provides a mechanism where changes in translation quality control in response to physiological cues can directly modulate bacterial persistence.
Wood WN, Mohler K, Rinehart J, Ibba M. 2021. Deacylated tRNA accumulation is a trigger for bacterial antibiotic persistence independent of the stringent response. mBio 12:e01132-21. https://doi.org/10.1128/mBio.01132-21
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