Large mutational target size for rapid emergence of bacterial persistence

Abstract

Phenotypic heterogeneity displayed by a clonal bacterial population permits a small fraction of cells to survive prolonged exposure to antibiotics. Although first described over 60 y ago, the molecular mechanisms underlying this behavior, termed persistence, remain largely unknown. To systematically explore the genetic basis of persistence, we selected a library of transposon-mutagenized Escherichia coli cells for survival to multiple rounds of lethal ampicillin exposure. Application of microarray-based genetic footprinting revealed a large number of loci that drastically elevate persistence frequency through null mutations and domain disruptions. In one case, the C-terminal disruption of methionyl-tRNA synthetase (MetG) results in a 10,000-fold higher persistence frequency than wild type. We discovered a mechanism by which null mutations in transketolase A ( tktA ) and glycerol-3-phosphate (G3P) dehydrogenase ( glpD ) increase persistence through metabolic flux alterations that increase intracellular levels of the growth-inhibitory metabolite methylglyoxal. Systematic double-mutant analyses revealed the genetic network context in which such persistent mutants function. Our findings reveal a large mutational target size for increasing persistence frequency, which has fundamental implications for the emergence of antibiotic tolerance in the clinical setting.

Biofilm-Related Infections: Bridging the Gap between Clinical Management and Fundamental Aspects of Recalcitrance toward Antibiotics

“…Conversely, the ofloxacin tolerance of planktonic bacteria was likely due to a mechanism other than the SOS response, since a ⌬recA mutant did not significantly impair the overall tolerance of either nonstarving or starving populations. The latter results strengthen the notion that induction of ofloxacin tolerance in starving biofilms is likely to involve mechanisms different from those currently described for planktonic cells (143,144).…”

The Formation of Streptococcus mutans Persisters Induced by the Quorum-Sensing Peptide Pheromone Is Affected by the LexA Regulator

“…The role of carbohydrate metabolism has been previously associated with the formation of persisters (59,60). Based on our results, we can hypothesize that a lack of LexA derepresses a gene(s) involved in the downregulation of the scrA gene contributing to the reduced persister levels.…”

Isolation of Highly Persistent Mutants of Salmonella enterica Serovar Typhimurium Reveals a New Toxin-Antitoxin Module

“…In general, these attempts revealed genes that likely only indirectly affect persistence. More recently, a high-density library of transposon insertion mutants was screened to identify new high persisters (31). Consistent with other studies, several different genes with diverse functions answered the selection for antibiotic tolerance (31).…”

“…Transposon mutant libraries have also been screened to identify mutations that cause either decreased or increased persistence in E. coli (31)(32)(33) and Pseudomonas aeruginosa (34). In general, these attempts revealed genes that likely only indirectly affect persistence.…”