(372e) Controlling Intracellular Mutagenesis for Targeted Therapeutic Strategies Against Antibiotic Resistance

Antibiotic resistance is a global health crisis that poses a significant threat to the medical progress achieved over the past century. Bacterial cells are capable of rapidly evolving resistance to antibiotics, in part due to the error-prone DNA repair mechanisms of the SOS response, which is activated in response to DNA damage. While the SOS response is a fundamental survival strategy that maintains bacterial genomic integrity, its mutagenic processes can lead to the formation of antibiotic-resistant cells. Therefore, a thorough understanding of mutagenic mechanisms is necessary to develop effective clinical treatment strategies to combat the global health crisis of antibiotic resistance. This study aimed to shed light on these mechanisms by perturbing the SOS response with mutagenic agents such as UV radiation and DNA damaging conventional antibiotics. Using an Escherichia coli promoter library, we established a high-throughput screening methodology and identified several genes, including recA, recN, rmuC, polB, and dinB, that showed an increase in expression levels in response to DNA damage (Fig. 1a). Deleting some of these genes individually or in combination led to a substantial reduction in intracellular mutagenesis. recA, the global regulatory gene of the SOS response, showed the highest upregulation during treatment and further experiments revealed a positive correlation between the level of recA expression and the degree of mutant formation. Our findings were further supported by investigating the effect of selected inhibitors that suppressed recA induction by inhibiting cellular transcription, translation of DNA repair genes, and/or ATP production, crucial for the energy-intensive SOS response pathway. Treatment with these inhibitors led to a significant reduction in UV-induced mutagenesis. In an attempt to translate these findings into clinically relevant therapeutic measures against antibiotic resistance, E. coli cells were co-treated with a conventional fluoroquinolone (ciprofloxacin), and metabolic inhibitors, including chlorpromazine, chloramphenicol, and arsenate. The fluoroquinolone that is specifically known to induce the SOS response was not able to cause mutagenesis in the presence of these inhibitors with a prominent decrease in recA expression level of the co-treated E. coli cells (Fig. 1b, c). Overall, our study highlights the importance of understanding and controlling intracellular mutagenesis in the context of antibiotic resistance and targeting the SOS regulatory network as a potential therapeutic adjuvant in combination therapies against antibiotic resistance.