| 论文摘要： |
Aeromonas salmonicidais a gram-negative bacterium that is the causative agent of furunculosis. AnA. salmonicidastrain was isolated from diseased turbot (Scophthalmus maximus) with the sign of furunculosis from North China. Based onvapAgene, the strain was further classified asA. salmonicidasubsp.masoucidaRZ6S-1. Culturing RZ6S-1 strain at high temperature (28 degrees C) obtained the virulence attenuated strain RZ6S. Genome sequence comparison between the two strains revealed the loss of the type IV secretion system (T4SS) and type III secretion system (T3SS) from the native plasmid pAsmB-1 and pAsmC-1 of wild-type strain RZ6S-1, respectively. Further study demonstrated that the wild-type strain RZ6S-1, but not its derivative mutant RZ6S, can stimulate apoptosis. Elevated protein level of cleaved caspase-3 was detected from epithelioma papulosum cyprinid (EPC) cells infected with wild-type strain RZ6S-1 as compared with that infected with RZ6S strain. Meanwhile, the invasion of the mutant strain RZ6S was about 17-fold higher than the wild-type strain RZ6S-1, suggesting that some protein(s) fromA. salmonicidasubsp.masoucidaRZ6S-1 suppress its invasion. The RZ6S mutant strain was attenuated, since its LD(50)is over 10,000 times higher compared to the wild-type strain as revealed in the turbot infection model. |
