Project description:Klebsiella variicola, traditionally considered a plant-associated species, is now recognized as an emerging foodborne and opportunistic pathogen at the human–animal–environment interface. Its ecological versatility, ability to colonize plants and food matrices, and increasing reports of antimicrobial resistance make this bacterium a growing concern for both public health and food safety. As the demand for alternative and clean-label antimicrobial strategies intensifies, essential oils (EOs) have gained attention for their broad biological activities and multi-target mechanisms. Among these, basil (Ocimum basilicum) essential oil (BEO), rich in linalool and phenylpropanoids, exhibits antimicrobial activity primarily through membrane disruption, metabolic interference, and oxidative imbalance. Despite the expanding use of plant-derived antimicrobials, the cellular response of K. variicola to EOs remains largely unexplored. To address this gap, this study employed a label-free quantitative proteomic approach to characterize the global response of K. variicola to a subinhibitory concentration of BEO. Exposure to BEO markedly affected proteins involved in membrane homeostasis, oxidative stress management, and translation processes. The concurrent repression of energy-related pathways and activation of antioxidant defences indicates that BEO imposes multifactorial physiological stress rather than acting through a single inhibitory target. These findings provide the first proteome-level insight into EO action against K. variicola and highlight molecular vulnerabilities that may reduce its persistence in food-processing environments. Overall, this study supports BEO as a promising natural antimicrobial and offers novel mechanistic clues on how emerging Klebsiella species respond to plant-derived stressors.
