Abstract 1530 Integrated effect of L-arabinose and stress-responsive signaling on E. coli antibiotic sensitivity

As bacterial infections become an ever-growing global concern, antibiotic tolerance research is more important than ever to protect human health. Continued investigation of bacterial responses to antibiotic mechanisms and conditions will improve clinical understanding of antibiotic treatments and provide a broader pharmaceutical toolbox for synergistic use of current antibiotics. Addition of exogenous L-arabinose in Escherichia coli (E. coli) cultures impacted antibiotic tolerance across several classes of antibiotics and experimental protocols compared to vehicle control. Arabinose enters E. coli central metabolism in the pentose phosphate pathway and is utilized as a carbon source in metabolic processes. Using minimum inhibitory concentration (MIC), disk diffusion, and minimal duration of killing (MDK99) assays, we investigated how the presence and absence of arabinose impacted bacterial growth at 37 °C for normal growth and 47.5 °C for heat shock conditions. We also examined if globally modulating the transcriptome by overexpressing transcription factors known to sensitize bacteria to chemical stressors also influenced the susceptibility of the bacteria to certain antibiotics. We used the PHL628 strain of E. coli because of its high selectivity under the kanamycin cassette and exogenously overexpressed two transcription factors, RpoH and RpoF, responsible for activating the heat shock response and late-stage flagella development, respectively. Our antibiotics of interest included vancomycin (a glycopeptide), levofloxacin (a quinolone), chloramphenicol, and tetracycline. In general, we see that arabinose provides a protective effect, allowing for bacterial growth to withstand higher concentrations and exposure time to antibiotics. The exception to this is when RpoH is constitutively active, demonstrating the opposite trend and suggesting that the activity of the transcription factor outweighs the effect of the arabinose. These experiments offer valuable insights into understanding the relationships between signaling pathways, metabolism, and antibiotic tolerance of E. coli. Funding is supported by Oberlin College, the Research Corporation for Science Advancement, and the National Science Foundation (MCB-2226953).