Basil Essential Oil as a Food Safety Hurdle Against Klebsiella variicola: Proteomic Insights into Impaired Replication and Translation

Klebsiella variicola is an emerging foodborne pathogen of growing concern due to its ecological versatility and ability to persist under adverse environmental conditions. Its widespread occurrence in plants, soils, insects, aquatic environments, and clinical settings, together with its detection in fresh and minimally processed foods, highlights the need to better understand its response to natural antimicrobial hurdles for improved food safety management. In this study, the response of K. variicola KV7 to sublethal exposure to basil essential oil (BEO) was investigated using label-free quantitative proteomics, with the aim of identifying physiological adaptations associated with survival under food-related stress. A total of 64 proteins were differentially expressed following treatment, indicating a broad cellular response even at low BEO concentrations. Beyond alterations in central metabolism, oxidative stress response, and membrane- associated functions, a key finding was the impact on informational processes. In particular, proteins involved in DNA replication and repair were affected, including the downregulation of DNA polymerase I, suggesting a reduced capacity to maintain genome integrity under stress conditions relevant to food environments. Moreover, BEO exposure significantly repressed several translation- related proteins, including elongation factor Tu (EF-Tu), an EF-P-like factor, and peptide chain release factor 2, indicating impaired translational efficiency and potential ribosomal dysfunction. Such effects may limit the synthesis of proteins required for growth, stress adaptation, and persistence in food matrices. Overall, these findings suggest that BEO acts not only as a membrane-active antimicrobial but also interferes with essential cellular processes required for adaptation and survival. This multifaceted mode of action may reduce the ability of the pathogen to persist in food-related environments. In conclusion, BEO exerts a pleiotropic stress on K. variicola, targeting DNA replication and protein synthesis. These results support the potential of BEO as a clean-label preservation strategy against emerging foodborne pathogens.