SanA is an inner membrane protein mediating the early stages of Salmonella infection

Abstract

AbstractBacterial membrane proteins, crucial for the interaction with the environment, encompass various functional molecules such as SanA. SanA is pivotal for the physicochemical properties of the bacterial membrane, influencingSalmonella’s antibiotic resistance and infection phenotype. Previous studies identified a link betweensanAmutation and increasedSalmonellainvasiveness, but the mechanisms underlying this phenomenon remain largely unexplored. Therefore, our research investigates SanA’s role duringSalmonellainfection, examining its expression pattern, localization within the cell, and association withSalmonellaPathogenicity Island I (SPI-I). Using subcellular fractionation and Western Blotting we revealed that SanA is predominantly located in the inner membrane. Additionally, we utilized transcriptional fusion to monitor SanA expression under various environmental conditions. We observed that SanA plays a significant role during the late exponential and early stationary growth phase and remains important 24 hours after the bacteria enter host cells. Moreover, our invasion assays demonstrated that deletion ofsanAin bacteria grown to early stationary phase significantly enhances their invasiveness, partly due to increased SPI-I expression, which is regulated in a nutrient availability-dependent manner. Our results highlight SanA’s essential role inSalmonella’s response to environmental stress, critical for its entry and survival in hostile environments. This research underscores the importance of inner membrane proteins in bacterial pathogenicity, particularly in the initial stages of infection.