Beyond Respiration: Heme A Synthase (CtaA) Orchestrates Hydrogen Sulfide Production and Virulence via Metabolic Reprogramming in Staphylococcus aureus

Endogenous hydrogen sulfide (H ₂ S) serves as a pivotal gasotransmitter conferring antimicrobial resistance and shielding bacteria from oxidative stress. While cystathionine γ-lyase (CSE)-dependent H ₂ S production is critical for Staphylococcus aureus survival, the upstream regulatory nodes linking metabolic status to H ₂ S-mediated redox defense remain elusive. Here, we identify heme A synthase (CtaA) as a master regulator that couples respiratory metabolism with H ₂ S biosynthesis, specifically under glucose-depleted conditions mimicking host niches such as abscesses and phagosomes. Using a Himar1 transposon screen followed by a high efficiency detection method, we demonstrate that CtaA deficiency precipitates a catastrophic collapse in H ₂ S levels (<10% of wild-type), leading to severe virulence and antimicrobial resistance changes. Specifically, the Δ ctaA mutant exhibits attenuated hemolytic activity and significantly reduced virulence in a Galleria mellonella model, despite displaying paradoxical resistance to specific antimicrobials.

Mechanistically, CtaA deletion triggers a maladaptive metabolic reprogramming characterized by the downregulation of the L-cysteine transporter TcyP and dysregulation of arginine metabolism, which collectively impair the bacterium’s capacity to produce endogenous H ₂ S to defense oxidative stress. Notably, this redox vulnerability is linked to altered endogenous nitric oxide (NO) dynamics, suggesting a disrupted H ₂ S-NO crosstalk essential for stress adaptation. Our findings elucidate a novel metabolic-redox axis where CtaA governs H ₂ S homeostasis to counteract host-imposed oxidative stress. Targeting the CtaA-H ₂ S axis represents a promising therapeutic strategy to sensitize S. aureus to host immune clearance by dismantling its critical redox shield.