Time-resolved sampling at 20- and 40-minutes post-exposure captured early transcriptional responses and subsequent protein and metabolic adaptations. Although the treatment was subinhibitory, it induced a pronounced reduction in viability, with a 45–50% decline in E. coli and an 18.9% decrease in S. aureus colony-forming units. In wild-type E. coli, transcriptomic profiling revealed robust activation of stress response pathways involved in efflux pump regulation and membrane remodeling, whereas the ampicillin-resistant strain exhibited minimal transcriptional perturbations, suggesting an attenuated stress perception. Proteomic analyses further demonstrated upregulation of molecular chaperones and proteins associated with envelope fortification, while metabolomic profiling uncovered shifts in osmoprotective compounds and TCA cycle intermediates indicative of an orchestrated antibacterial response. Lipidomic assessments corroborated these findings by revealing increased formation of cyclopropane fatty acids in E. coli and branched-chain fatty acid modifications in S. aureus. These adaptations are known to stabilize membrane fluidity under stress. Collectively, these convergent multi-omics signatures define a membrane-centric mode of action for QPAL and highlight strain-specific adaptive strategies. Our results establish a mechanistic foundation for the potential of QPAL as a sustainable, lignin-derived antimicrobial scaffold and support its further development in combination with conventional antibiotics.
Funding: NIH MIRA Grant number 5R35GM143009 and Nebraska Research Collaboration Initiative Grant.