Objective  Bile is an important signaling molecule that regulates the intestinal microflora and environment in both directions, playing an important role in viral and bacterial infections. CRP (cAMP receptor protein) is involved in the bile tolerance of Escherichia coli and Salmonella in infections. In this study, we evaluated the effect of CRP (cAMP receptor protein) on bile tolerance of Aeromonas hydrophila.

  Methods  The luxS-deleted, crp-deleted and crp-complemented strains of A. hydrophila were constructed, and the bile tolerance of A. hydrophila and its constructed strains was detected by bile growth experiments.

  Results  The growth rates of A. hydrophila strains BJ018, BJ018ΔluxS and BJ018Δcrp in Luria broth (LB ) were similar. However, in 10% bile LB, the growth of BJ018 and BJ018ΔluxS was inhibited in the first 8 hours, and the growth rate was logarithmic in the later stage; while the growth rate of BJ018Δcrp was higher than that of the wild strain, and the early growth was not inhibited. The early growth of the complemented strain BJ018Δcrp-pSRK-crp was re-inhibited in the early stage, which was similar to that of the wild strain BJ018 containing plasmid pSRK. The other A. hydrophila strains BJ017, BJ054 and their crp-deleted strains had the same result with BJ018 and BJ018Δcrp. The result suggested that CRP had influence on bile tolerance of A. hydrophila.

  Conclusion  CRP negatively regulated the growth of A. hydrophila in bile and might play an important role in bile tolerance regulation.