Biological Characteristics And Application Of Bdellovibrio Sp. Isolated From Brackish Water Of Pearl River

Bdellovibrio is an obiligate predator that replicates inside a wide range of bacterial prey. Bdellovibrios have been found in fresh water, sewage, sediment, soil and rhizosphere, they can penetrate into the cell wall of prey and replicate in the periplasmic space, making the prey lysed eventually. Thanks to the Bdellovibrio's unique biological characteristics of parasitic ability and wide prey range, as a biological reagent compared with side-effect inducing antibiotics, it will be a wise choice of using Bdellovibrios to eliminate or suppress the pathogens. Most documents have been focusing on the study of Bdellovibrios isolated from sea or fresh water, but no report on the Bdellovibiros isolated from low salinity environment. Three plaque-forming bacteria were isolated from a low salinity river in GuangDong Province based on double-agar technique and using (E.coli)DH5αas host. With the isolation of Bdellovibrios from low salinity environment, the feasibility of potential application in food safety area and anti-pathogens of aquaculture will be investigated with the knowledge of biological characteristics of the isolated Bdellovibirios.In our investigation on seawater obtained from low salinity environment in Guangdong Provice, three bacteria (named DLR-L, DLR-M and DLR-S respectively) which could prey on (E.coli)DH5αwere isolated through DNB double layer agar plating technique. These three strains were identified, according to"Bergey's manual identification of bacteria"(ninth edition), as Bdellovibrio sp. through observing the plaques formed in the DNB double layer agar plate and their morphological properties by transmission electron microscopy.The lysis experiments on 44 pathogens or potential pathogens showed that individual DLR-L,DLR-M and DLR-S lysed 72.7%,65.9% and 70.5% of the total bacteria, respectively.In the Salmonella typhimurium elimination test, the fillet of tilapia were used as the material of the experiment. The equivalent of ten times and the equivalence of the Salmonella typhimurium's concentration of DLR-M's concentrated liquid were added to eliminate Salmonella typhimurium. The pH value, the quantity of DLR-M, the total count and the quantity of disease-causing bacteria were detected. The result showed that, Bdellovibrio had obvious effect on preserving the fillet. The shelflife of the fillet extended more than 12 hours after adding DLR-M's concentrated liquid and the effect of adding the equivalence of the Salmonella typhimurium's concentration of DLR-M was better than adding ten times. The pH value of the surface of the fillet changed little after adding DLR-M's concentrated liquid. The effect of restraining the total count and the quantity of disease-causing bacteria mainly happened in the first 12 hours. After 12 hours, the total count and the quantity of disease-causing bacteria increased quickly beause of the decline of the number of Bdellovibrio. Adding the DLR-M's concentrated liquid, the total count and the quantity of disease-causing bacteria were less in the whole process. It was indicating the good potential value of application in food safety area.