Protein expression and morphological adaptations of Campylobacter jejuni under prolonged cold stress in chicken juice.

Campylobacter jejuni is a foodborne pathogen with limited ability to thrive at low temperatures. This study investigated the survival and proteomic responses of C. jejuni NCTC 11168 during prolonged storage at 4 °C, with specific focus on its behavior in chicken juice. An initial rapid decrease of 80-90 % in viable cell counts across various broth media was observed within the first 10 days; however, chicken juice provided the most conducive environment for slowing the decline in cell viability compared to Brain Heart Infusion Broth (BHI) and Mueller Hinton (MH) broths. Electron microscopy revealed morphological transitions from spiral to coccoid forms over time, indicative of a stress adaptation strategy. Proteomic analysis identified 50 upregulated and six downregulated proteins, with key enriched functional categories including translation, ribosomal biogenesis, energy metabolism, cell envelope biogenesis, and motility. KEGG pathway analysis highlighted significant changes in metabolic pathways, flagellar assembly, and bacterial secretion systems. A protein-protein interaction network revealed clusters associated with ribosomal function, cell envelope maintenance, and motility. The acidic periplasmic protein Cj0424 (8.92-fold), previously linked to biofilm formation and oxidative stress response, was the most upregulated protein. Notably, no virulence-associated proteins were detected under cold storage conditions. These findings suggest that C. jejuni employs a multifaceted stress response to low temperatures, enhancing its persistence in food matrices and posing a potential transmission risk.