Abstract:[Background] As a relatively new member of marine probiotics, Bdellovibro-and-like organisms (BALOs) have a wide application prospect. However, because of BALOs’ special reproductive mode and cycle, the pratical application of BALOs is greatly affected by their parasitic host characteristics and biological activities. Therefore, selecting appropriate parasitic hosts and maintaining the activity of BALOs preparation are very important for BALOs’ application. [Objective] to isolate a strain of BALOs which can use gram-positive probiotics Bacillus subtilis as host, and increase its Bdelloplast concentration in the culture for storage. [Methods] Bacillus subtilis was used as host bacterium to isolate BALOs from sea mud samples from Hainan by DNB (Dilute nutrient broth) double plate method. Transmission electron microscope and partial 16S rRNA gene sequence analysis were conducted to identify the Bdellovibrio strain, and its biological characteristics and lysis spectrums were studied. In addition, the effects of ampicillin, indole, Ca2+ and Mg2+ on the formation of bdelloplast were researched. [Results] A strain of BALOs (named BDE-1) which could prey on Bacillus subtilis was isolated and identified successfully. The optimal temperature, salinity and pH for BDE-1 were 25 °C, 2.0% and 7.0 respectively. Lysis experiments on 28 pathogenic or potential pathogenic strains showed that BDE-1 lysed 24 strains, corresponding to 85.7% of lysis rate. For the 13 strains of tested vibrios, its lytic rate was as high as 92.3%. While all four factors (indole, ampicillin, Ca2+ and Mg2+) promoted bdelloplast formation, the promotion effect of indole and Ca2+ was more significant. [Conclusion] This study not only provided a feasible solution for the optimal selection of parasitic hosts of Bdellovibro, but also provided a theoretical basis for the maintenance or enhancement of the application of Bdellovibro probiotic preparation.
