Identification of Differentially Regulated Edwardsiella ictaluri Proteins During Catfish Serum Treatment

Edwardsiella ictaluri is a facultative, intracellular, gram-negative bacterium that causes enteric septicemia of catfish (ESC). Edwardsiella ictaluri is known to be resistant to defense mechanisms present in catfish serum, which might aid in its use of a host's bloodstream to become septicemic. However, the precise mechanisms of the survival of E. ictaluri in host serum are not known. Analysis of the response of E. ictaluri to the host serum treatment at a proteomic level might aid in the elucidation of its adaptation mechanisms against defense mechanisms present in catfish serum. Thus, the objective of this study was to identify differentially regulated proteins of E. ictaluri upon exposure to naïve catfish serum. Two-dimensional difference gel electrophoresis (2D-DIGE) followed by in-gel trypsin digestion and MALDI-TOF/TOF analysis were used for identification of differentially expressed E. ictaluri proteins. A total of 19 differentially regulated proteins (7 up- and 12 downregulated) were identified. Among those were four putative immunogenic proteins, two chaperones and eight proteins involved in the translational process, two nucleic acid degradation and integration proteins, two intermediary metabolism proteins, and one iron-ion-binding protein. Further research focusing on the functions of these differentially expressed proteins may reveal their roles in host adaptation by E. ictaluri.