Phenotype, Virulence and Immunogenicity of Cyclic AMP Receptor Protein (Crp) Mutants in Catfish Host.

, a facultative aerobic pathogen belonging to the Enterobacteriaceae family, is the etiological agent of edwardsiellosis that causes significant economic loses in the aquaculture industry. cAMP receptor protein (CRP) is one of the most important transcriptional regulators, which can regulate large quantities of operons in different bacteria. Here we characterize the gene and report the effect of a deletion in . The -deficient mutant lost the capacity to utilize maltose, and showed significantly reduced motility due to the lack of flagella synthesis. We further constructed a ΔP mutant to support that the phenotype above was caused by the crp deletion. Evidence obtained in fish serum killing assay and competitive infection assay strongly indicated that the inactivation of impaired the ability of to evade host immune clearance. More importantly, the virulence of the mutant was attenuated in both zebrafish and channel catfish, with reductions in mortality rates. In the end, we found that mutant could confer immune protection against infection to zebrafish and channel catfish, indicating its potential as a live attenuated vaccine.