New insights into the stress response mechanisms of stress-resistant <i>Listeria monocytogenes</i> via multi-omics and cell morphological changes

<i>Listeria monocytogenes</i> (<i>Lm</i>) can persist in stressful conditions such as low pH, temperature, and salt concentration. Omics approaches enable the investigation of biomolecular features at both the transcript and protein levels. This study aimed to understand stress response mechanisms by analyzing transcript and protein levels of stress-resistant <i>L. monocytogenes</i> (SR-<i>Lm</i>) under multiple stress conditions. RNA sequencing was performed at 4, 8, 12, 24, and 48 h growth under a multiple stress condition (pH 3 + 1 °C + 5% salt) and RT-qPCR was also conducted. Gene expression analysis revealed upregulation of the <i>yebS</i>, <i>tsx, secA, gap, gtfA</i>, along with several stress-related genes (<i>cspB</i>, <i>cspD</i>, <i>spxA</i>, and <i>cysK</i>) during 48 h. Protein expression profiles of SR-<i>Lm</i> were conducted under (1) 5% salt+1 °C, (2) pH 3 + 1 °C, and (3) pH 3 + 1 °C + 5% salt conditions at 4 and 12 h. Some proteins including Gap, Eno, Citz, and PurM were upregulated in both analyses, potentially associated with stress-related biomarkers. KEGG pathway analysis was performed using proteomic data to predict stress response mechanisms including chaperone, glycolysis, and glutamate decarboxylase system (GAD). Cell morphology under stress and normal conditions was observed, with some elongated, thin, and bumpy cell shapes under acid and multiple stress conditions. This study provides new insights into the stress response of SR-<i>Lm</i>, enhancing the understanding of how <i>Lm</i> survives in adverse food processing and storage environments.