Untargeted and targeted transcriptome analysis to decipher the impact of exogenous fatty acids in cold stress adaptation of Listeria monocytogenes

Listeria monocytogenes is a ubiquitous and psychrophilic foodborne pathogen commonly found in raw materials, ready to eat products and food environments. It was previously demonstrated that L. monocytogenes can grow faster at low temperature when unsaturated fatty acids (UFA) are present in its environment. In this study, we used comparative gene expression profiling of RNA-sequencing data to understand the impact of UFA on the behavior and cold adaptation of L. monocytogenes. We demonstrate that the incorporation of UFA into the membrane induces changes in the regulation of overall fatty acid biosynthesis, which prompts us to propose two hypotheses for UFA synthesis in L. monocytogenes. The general stress response is also highly impacted by the incorporation of UFA into the membrane at low temperature. In particular, we hypothesize that transcriptional regulation of cspB is not a temperature dependent mechanism, but could be related to a membrane fluidity stimulus. Furthermore, when UFA are incorporated into the membrane at low temperature, we observed overexpression of genes involved in flagella assembly. This study sheds light on the cold adaptation of L. monocytogenes in the presence of exogenous FA and on potential concerns for controlling these bacteria in food environments. Overall design: To investigate the impact of the presence of exogenous unsaturated fatty acid (18:1) at low temperature on gene expression profile of Listeria monocytogenes Lm208, we performed gene expression profile analysis using data obtained from RNA sequencing of L. monocytogenes grown in four growth conditions at one time point (mid-exponential phase). Comparative gene expression profiling of RNA-seq data for L. moncotyogenes Lm208 strain grown without (C) or with fatty acid supplementation (FA) at two temperature 37°C (C37 and FA37) or 5°C (C5 or FA5) in tritplicates.