Within bacterial populations, a small fraction of persister cells is transiently capable of surviving exposure to lethal doses of antibiotics. As a bet-hedging strategy, persistence levels are determined both by stochastic induction and by environmental stimuli called responsive diversification. Little is known about the mechanisms that link the low frequency of persisters to environmental signals. Our results support a central role for the conserved GTPase Obg in determining persistence in Escherichia coli in response to nutrient starvation. Obg-mediated persistence requires the stringent response alarmone (p)ppGpp and proceeds through transcriptional control of the hokB-sokB type I toxin-antitoxin module. In individual cells, increased Obg levels induce HokB expression, which in turn results in a collapse of the membrane potential, leading to dormancy. Obg also controls persistence in Pseudomonas aeruginosa and thus constitutes a conserved regulator of antibiotic tolerance. Combined, our findings signify an important step toward unraveling shared genetic mechanisms underlying persistence.

Persisters are transiently antibiotic-tolerant cells that complicate the treatment of bacterial infections. Both theory and experiments have suggested that persisters facilitate genetic resistance by constituting an evolutionary reservoir of viable cells. Here, we provide evidence for a strong positive correlation between persistence and the likelihood to become genetically resistant in natural and lab strains of E. coli. This correlation can be partly attributed to the increased availability of viable cells associated with persistence. However, our data additionally show that persistence is pleiotropically linked with mutation rates. Our theoretical model further demonstrates that increased survival and mutation rates jointly affect the likelihood of evolving clinical resistance. Overall, these results suggest that the battle against antibiotic resistance will benefit from incorporating anti-persister therapies.

The evolution of antibiotic resistance is a major threat to society and has been predicted to lead to 10 million casualties annually by 2050(1). Further aggravating the problem, multidrug tolerance in bacteria not only relies on the build-up of resistance mutations, but also on some cells epigenetically switching to a non-growing antibiotic-tolerant 'persister' state(2-6). Yet, despite its importance, we know little of how persistence evolves in the face of antibiotic treatment(7). Our evolution experiments in Escherichia coli demonstrate that extremely high levels of multidrug tolerance (20-100%) are achieved by single point mutations in one of several genes and readily emerge under conditions approximating clinical, once-daily dosing schemes. In contrast, reversion to low persistence in the absence of antibiotic treatment is relatively slow and only partially effective. Moreover, and in support of previous mathematical models(8-10), we show that bacterial persistence quickly adapts to drug treatment frequency and that the observed rates of switching to the persister state can be understood in the context of 'bet-hedging' theory. We conclude that persistence is a major component of the evolutionary response to antibiotics that urgently needs to be considered in both diagnostic testing and treatment design in the battle against multidrug tolerance.