Hfq balances energetic efficiency and antibiotic persistence in <i>Acinetobacter baumannii</i>

The RNA chaperone Hfq of <i>Acinetobacter baumannii</i> has been documented in altering antibiotic susceptibility and other optimal stress tolerance capabilities of this pathogen. However, the understanding of whether and how Hfq impacts antibiotic persistence remains unexplored in <i>A. baumannii</i>. Consequently, we show that energetic burden on Δ<i>hfq</i> cells is imposed due to perturbation of the global transcription of genes, including ones involved in metabolism, secretion systems, and electron transport. As a result, actively growing Δ<i>hfq</i> cells demonstrate better survival in the presence of antibiotics with an increased spontaneous persistence phenotype compared with wild-type (WT) cells in the presence of cefepime. Introducing a chromosomal Hfq variant with a mutation in its proximal RNA-binding face (Hfq_F39A) resulted in an intermediate effect on growth fitness and cefepime persister frequency compared with WT and Δ<i>hfq</i>. Additionally, the Hfq_F39A persisters exhibit a disrupted proton motive force along with lower metabolic activity and reduced intracellular ATP. Importantly, both Δ<i>hfq</i> and Hfq_F39A strains were less virulent than WT; however, they exhibited better relative survival in murine lungs compared with the WT when treated with cefepime. However, our findings indicate that although <i>hfq</i> deletion increases spontaneous persister frequency against cefepime <i>in vitro</i>, its attenuated virulence results in lower organ burden <i>in vivo</i>. Hence, highlighting the fact that although targeting Hfq may contribute to increased persistence, its reduced organ burden makes it a clinically relevant drug target.IMPORTANCEThis study demonstrates the significance of Hfq in modulating physiology and antibiotic persistence of <i>Acinetobacter baumannii</i>. By comparing the <i>hfq</i> deletion mutant with wild-type <i>A. baumannii</i>, we uncovered a persistence mechanism that increases the survival of this pathogen, particularly under cefepime stress, through pleiotropic dysregulation of post-transcriptional networks impacting cellular energetics. In Δ<i>hfq</i> strains, the elevated expression of energy-intensive genes (such as those for Type VI and II secretion systems), along with the suppression of metabolic and electron transport pathways, leads to increased persister frequencies. This illustrates how Hfq impacts both growth and antibiotic persistence. Introducing an Hfq variant (Hfq_F39A) with impaired RNA binding showed an intermediate effect on growth and persistence, further implicating Hfq functionality in antibiotic persistence. Overall, these findings provide a foundation for targeting Hfq in <i>A. baumannii</i> therapeutics, with implications for balancing reduced virulence against the risk of increased relative survival to frontline antibiotics, particularly in immunocompromised hosts.