Lysis Ability And Fermentation Conditions Of Bdellovibrio Sp. Isolated From Marine Environment

Bdellovibrio sp. is a kind of parasitic microorganism which can act as phage and demonstrate desirable ability in growing and reproducting by eliminating pathogenic bacterium. Bdellovibrios are capable of preying upon a wide range of bacteria, which indicates the broad application prospects of Bdellovibrio sp. in preventing aquaculture disease as a kind of microecologics.In this study, the Bdellovibrio strains TM1 and FM1we have used were isolated from the sea invironment by our lab. we firstly systematically explored the lysis spectrum of the two Bdellovibrio strains to 33 representative pathogens or potential pothogens. The lysis experiments showed that the strain FM1 can lyse 90.91% (30 of 33) of the bacteria tested, while the strain TM1 can lyse 75.76% (25 of 33). Which demonstrated that the strain FM1 were more capable than TM1. There were 2 bacteria (6.06%) can be lysed by neither strains, while 24 (72.73%) can be lysed by both strains. In combination, they lysed 93.94% of (31 of 33) the bacteria tested.Influences of pH, salinity, sodium glutamate, divalent cations (Ca2+ Mg2+), and the initial concentration of the host on the lysis ability of Bdellovibrio strain FM1, were studied in shaking flask scaled Fermentation. The Bdellovibrio strain FM1 was observed to show great ability in growing in a pH range of 6.8 to 8, reaching the optimum at pH 7. This strain had good activity in growing and lysing between the salinity range of 2% to 3%, with the optimal salinity level of 3%. And the sodium glutamate range of 1mmol/L to 5mmol/L, with the optimal salinity level of 3mmol/L. Appropriate concentration of Ca2+ and Mg2+ can enhance the growth and the lysis ability of FM1, but the enhancement won't last for long, the optimal level was 4mmol/L. After single factor experiment, orthogonal designed experiment of four factors, three levels was adopted to optimize the FM1 culture component. The optimum culture medium component obtained were pH 7.2; salinity 3%; concentration of sodium glutamate 2mmol/L; concentration of Ca2+ and Mg2+ 3mmol/L. Then the optimum reaction conditions of the fermentation were obtained by experiment were as follows: the incubation time was 36h; the initial concentration of FM1 was 1×104PFU/mL; the cultivation temperature was 28°C; the liquid volume was 150mL in 500mL flask. Under the optimum conditions, the concentration of FM1 could get 2.0×107PFU/mL in the 30L fermentor which was 2.8 times more than it did in the flask.