Alterations in Salmonella diarizonae proteome after exposure to human serum

Salmonella bacteria can modify structures of various cell envelope components to survive in extremely adverse environments and evade the host's immune response. Bacterial resistance to serum is crucial for the development of systemic infections. Here, we investigated how long-term exposure to human serum alters the length of lipopolysaccharide and the outer membrane proteome shape of Salmonella diarizonae. Experiments have shown that prolonged exposure to human serum affects the survival rate of S. diarizonae but not the average length of lipopolysaccharide. Interestingly, after the analysis of preparations of outer membrane proteins we have shown, that multiple passages in human serum induced changes in the outer membrane proteome. Among the proteins with higher abundance compared to the strain prior to serum exposure, proteins described as complement resistance proteins of Salmonella bacteria could be identified (PagC, PgtE). Additionally, an upregulation of proteins involved in the biosynthesis of polysaccharides (RfbD, RfbA, RfbF, YaeD, PmrF, WzzE) was observed, suggesting that modifications in the structure of lipid A and modifications in the length of the enterobacterial common antigen (ECA) may be involved in the protection of S. diarizonae from the bactericidal action of human serum.