Inhibitory Effects of Bacteriophages on the Growth of Vibrio sp., Pathogens of Shrimp in the Indian Aquaculture Environment

摘要

Bacteriophages of Vibrio harveyi from a shrimp farm located at Tuticorin, Tamilnadu, India, were isolated, characterized and identified. The phages, when examined by electron microscopy , were found to have icosahedral morphology. The phages belong to the Siphoviridae family and were designated VH1 to VH8. They produced circular clear plaques of growth inhibition on Vibrio sp., plate cultures. The growth inhibitory effects of the bacteriophages on isolates of V. harveyi were screened by a one-step agar bioassay method and the results suggest that the infectivity of the V. harveyi phages was not affected by ribonuclease, protease, trypsin, chloroform, acetone, ethyl alcohol, methyl alcohol and Triton-X100 treatment at 37?°C. Even after their storage in chloroform or DMSO (dimethyl sulfoxide, 7%) at -40?°C. They showed 100% infectivity and plaque-forming ability. In contrast, Infectivity of the V. harveyi phages was affected by lysozyme and SDS and in these cases; plaques were not formed on agar plate assays. The phages were found to be stable over the pH range 6-11 and exhibited optimal survival at 37?°C while complete inactivation occurred at temperatures exceeding 55?°C. All the isolates of bacteriophage (VH1-VH8) initiated an infection cycle and caused lysis of the host bacterial cells within 2 h from the start of incubation. The propagation curve for each phage shows a burst time started from 1-10 h. The results suggest that bacteriophages of Vibrio sp., might be effectively used in vivo as biological agents to control these pathogenic bacteria in aquaculture systems.