Beyond dormancy: Active DNA repair and protein synthesis drive antibiotic tolerance and enable synergistic eradication.

The unresponsiveness of bacterial tolerant cells to antibiotics has been attributed to physiological dormancy triggered by environmental stresses. Interestingly, after a 24 - hour treatment, the tolerant cells became susceptible to ciprofloxacin and nitrofurantoin, which target DNA, as well as gentamicin, which targets protein synthesis, with distinct combinational effects. However, they remained resistant to ampicillin, which targets the cell wall. The mechanism study revealed that the activities of protein synthesis and DNA repair in tolerant bacteria formed during nutrient starvation remained at a high level and only gradually decreased during six days of starvation. Meanwhile, the reduction in energy production (ATP level), antioxidant defense (ROS level), and efflux functions led to an increased susceptibility of the bacterial tolerant subpopulation to antibiotics. These findings confirm that bacterial tolerant cells remain physiologically active, and inhibiting protein synthesis and DNA repair presents promising opportunities for combating bacterial tolerance with existing antibiotics.