Comparative transcriptome RNA-Seq analysis of Listeria monocytogenes with sodium lactate adaptation

Listeria monocytogenes is an important foodborne pathogen that can cause listeriosis with high mortality rates. Sodium lactate has been used as an antimicrobial in meat products to inhibit the growth of foodborne pathogens. However, the adaptation mechanism of L. monocytogenes to sodium lactate remains unclear. In this paper, the growth/survival of L. monocytogenes was determined in ready-to-eat (RTE) meats with 4% sodium lactate treatment. RNA-Seq was conducted to compare the transcriptional profiles between cells cultured in Brain Heart Infusion broth with and without 4% sodium lactate to identify differentially expressed genes (DEGs). DEGs (766) including 329 up-regulated and 437 down-regulated genes were identified from RNA-Seq analysis in response to sodium lactate treatment. RNA-Seq data were validated using quantitative reverse transcription PCR (qRT-PCR) assays. The DEGs include genes involved in pathways including signal transduction, ABC transporter and PTS systems. Interestingly, the DEGs involved in bacterial chemotaxis and flagellar assembly were exclusively down-regulated, indicating that flagellar synthesis was inhibited by sodium lactate treatment. Most importantly, virulence-related genes were induced, suggesting that sodium lactate may increase the virulence potential of L. monocytogenes. Our study provides insight on the adaptation mechanism of L. monocytogenes with treatment of sodium lactate, and may aid in searching for strategies that may have a synergistic effect in combination with sodium lactate to inhibit L. monocytogenes in RTE meat.