Transcriptome analysis suggests the cell wall as the primary target of the antilisterial effect of carrots.

Listeria monocytogenes is a serious foodborne pathogen. To prevent L. monocytogenes contamination, comprehensive hygiene protocols are implemented during food processing. Moreover, targeted antimicrobial interventions are desirable. Carrots have long been recognized for their antimicrobial effects against L. monocytogenes. However, the underlying mechanisms behind this effect have not been elucidated so far. In this study, we aimed to (i) identify the carrot accessions exhibiting the strongest antimicrobial effects from a selection of 52 different accessions and (ii) characterize the transcriptomic response of three L. monocytogenes strains to stress induced by carrot juice. After screening 52 different carrot accessions on L. monocytogenes, of which 19 killed 4-log(10) of L. monocytogenes within 3 min, we conducted a transcriptomic study using three highly effective carrot accessions to analyze gene expression changes in response to carrot juice exposure. Exposure to carrot juice caused significant changes in the expression of genes associated with the structure and integrity of the cell wall, two-component regulatory systems, and ABC transporters, highlighting the complex response of L. monocytogenes to carrot juice. Furthermore, we observed that several genes associated with nisin resistance were significantly differentially expressed in response to carrot juice stress.IMPORTANCEListeria monocytogenes is a major concern for food safety due to its remarkable resilience to a wide range of stress conditions in food matrices and food-processing environments. Given that carrots have previously been shown to exert antimicrobial effects against L. monocytogenes, we sought to further investigate this phenomenon. Our results demonstrate that carrot juice triggers differential expression of genes involved, among others, in maintaining cell wall structure and integrity. These findings suggest that carrots may represent a promising natural intervention strategy to mitigate L. monocytogenes contamination, aligning with the growing consumer demand for natural food additives.