|FANG, TING - Fujian Agricultural & Forestry University|
|SUO, YUJUAN - Ministry Of Science And Technology Of The People'S Republic Of China|
|GAO, SHIGANG - University Of Shanghai|
|BARANZONI, GIAN MARCO - Collaborator|
Submitted to: Frontiers in Microbiology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/23/2021
Publication Date: 12/23/2021
Citation: Liu, Y., Fang, T., Suo, Y., Gao, S., Baranzoni, G., Armstrong, C.M. 2021. Transcriptomics of Listeria monocytogenes treated with olive leaf extract. Available online: Frontiers in Microbiology.12:78116. https://doi.org/10.3389/fmicb.2021.782116.
Interpretive Summary: There is a need for novel methods to control pathogenic bacteria in the food industry. Olive leaf extract (OLE) is an herbal supplement that is beneficial to human health, and it also has antimicrobial properties against Listeria monocytogenes, a major foodborne pathogen that can cause serious human illness. However, mechanisms that contribute to the inhibition of growth of L. monocytogenes by OLE are unknown. RNA-Seq technology is a powerful tool that can be used to study the expression of all of the genes possessed by a bacterium under different conditions. RNA-Seq was used to study the expression of genes in L. monocytogenes when exposed to olive leaf extract (OLE). A number of genes were found to be affected by OLE treatment, and thus these genes could potentially be investigated as targets for antimicrobial treatments to control L. monocytogenes. Information from this study indicates that OLE has the potential to be used as a natural antimicrobial to control foodborne pathogens in food and the food environment.
Technical Abstract: Listeria monocytogenes is an important foodborne pathogen that can cause listeriosis, which is associated with high mortality rates. Olive leaf extract (OLE), a known plant antimicrobial, has been shown to inhibit the growth of foodborne pathogens such as L. monocytogenes although its mode of action against L. monocytogenes remains unclear. Therefore, the growth/survival of L. monocytogenes in the presence of OLE was evaluated and RNA-Sequencing (RNA-Seq) was subsequently performed on L. monocytogenes grown in the presence of a sub-lethal level of OLE (7.8 mg/ml) to elucidate its effects. Results obtained from cells cultured both with and without OLE at two different time points (3.5-hr and 24-hr) revealed 661 genes that were differentially expressed. Of the differentially expressed genes (DEGs) identified, transcription was altered for 171 genes in response to the 3.5-hr olive leaf extract treatments while 490 genes were altered in response to the 24-hr OLE treatment. These DEGs included but were not limited to genes encoding for signal transduction, ABC transporters, and the phosphotransferase transport system. Interestingly, several virulence-related genes were down-regulated including an ABC transporter permease previously shown to negatively regulate biofilm formation, genes involved in flagella assembly and binding/entry into host cells as well as those regulating acid resistance suggesting that olive leaf extract may decrease the virulence potential of L. monocytogenes. Furthermore, RNA-Seq data were validated using quantitative reverse transcription PCR (qRT-PCR) assays. Our study provides insight into the mode of action of OLE treatment against L. monocytogenes and may aid in identifying synergetic strategies to inhibit L. monocytogenes in food.