PEB3 and PEB2 are associated with serine-dependent changes in surface properties and host cell interaction in Campylobacter jejuni

Campylobacter jejuni relies on amino acids, particularly serine, for growth and host colonization. However, the molecular mechanisms linking serine availability to host-associated phenotypes remain unclear. In this study, we investigated the roles of the periplasmic ligand-binding proteins PEB3 and its homolog PEB2 in serine-dependent phenotypes. Surface plasmon resonance analysis showed that both proteins bind serine with high apparent affinity in vitro. Deletion of peb3 and peb2 resulted in impaired growth under serine-only conditions, reduced cell surface hydrophobicity, significantly decreased host cell-associated bacterial counts during the early stage of infection, and reduced IL-8 secretion by 30.6–77.8%. Exploratory correlation analysis suggested a positive association between cell surface hydrophobicity and host cell association. In addition, unlike the wild type, the peb3 / peb2 double-deletion mutant did not show increased host cell association under serine-only conditions compared with other amino acid conditions, suggesting a role for these proteins in serine-dependent host cell association. Together, these findings suggest that PEB3 and PEB2 are associated with serine-dependent growth and surface phenotypes as well as host cell interaction phenotypes, including reduced early host cell association, under the conditions tested. These results highlight a potential link between metabolic state and host-associated phenotypes in C. jejuni .