CRISPRi screening reveals <i>E. coli</i> ’s anaerobic-like respiratory adaptations to gentamicin: membrane depolarization by CpxR

Bacterial genes serve diverse cellular functions and many affect fitness in response to environmental challenges. We employed CRISPR interference screening to investigate the fitness effect of each gene in <i>Escherichia coli</i> exposed to gentamicin, aiming to understand the cellular defense mechanisms. Our findings revealed that ribosomal proteins, ribosome-associated proteins, toxin-antitoxin systems, and outer membrane proteins strongly influence the fitness of <i>E. coli</i> in gentamicin. Notably, gentamicin-induced fitness changes resembled those under anaerobic conditions, where resistance to gentamicin was observed. Specifically, genes related to the biosynthesis of cofactors and electron carriers, crucial for the respiratory system, showed reduced essentiality under both gentamicin and anaerobic conditions, suggesting a disruption in membrane potential leading to limited gentamicin uptake. Transcriptomic and genome-wide binding analyses identified the two-component system CpxR as a key regulator of respiratory systems in response to gentamicin. Our study provides insights into cellular defense mechanisms, offering potential strategies for combating antibiotic resistance.IMPORTANCEBacteria can adapt to a variety of stressful environments, including antibiotic exposure. The mechanisms underlying antibiotic resistance remain an active area of investigation. Clustered regularly interspaced short palindromic repeats (CRISPR) interference enables specific silencing of gene expression, allowing researchers to assess the fitness effects of gene knockdowns under given conditions. Using genome-wide CRISPR interference screening on <i>Escherichia coli</i> exposed to gentamicin, we identified anaerobic-like fitness effects of genes involved in respiration and the maintenance of membrane potential-key processes that facilitate gentamicin entrance into the cell. Transcriptomic analysis and immunoprecipitation assays further indicated that the two-component system CpxR modulates respiratory adaptations in response to gentamicin challenge. These findings shed light on the development of antibiotic resistance in bacteria and may offer new insight into strategies for treating gentamicin-resistant pathogens.