The two-component system histidine kinase LiaS contributes to the stress resistance and virulence of zoonotic Listeria monocytogenes
ABSTRACT LiaS is a histidine kinase receptor in two-component systems that senses environmental stress signals. This study investigated the roles of LiaS in Listeria monocytogenes stress resistance and virulence. Phenotypic assays showed that deletion of liaS (ΔliaS) resulted in significantly impaired growth under acidic, alkaline, and osmotic stresses, as well as reduced survival under strong acidic conditions. These defects were partially restored in the complemented strain (CΔliaS). The growth defects were also observed in the ΔliaS under Cu2+ or H2O2 exposure. Furthermore, the ΔliaS strain exhibited impaired invasion and intracellular migration in host cells, along with attenuated colonization in the liver and spleen at 24 h post-infection. Bacterial loads in the spleen of infected mice remained lower at 48 h. The mortality was also delayed in ΔliaS‑infected mice. Transcriptional analysis revealed that compared to neutral conditions, osmotic stress-related genes (except opucB and gbuC) were significantly upregulated in the ΔliaS strain under acidic conditions, indicating that LiaS modulates acid tolerance through transcriptional regulation. Collectively, LiaS is essential for the adaptation of Listeria monocytogenes to acidic, osmotic, and oxidative stresses. Its absence attenuates host cell invasion, intracellular motility, and organ-specific colonization, highlighting its dual role in environmental resilience and pathogenicity. These findings provide a theoretical basis for understanding host–pathogen interactions and offer new strategies against antimicrobial-resistant pathogens.