Transfection of Bdellovibrio bacteriovorus with bacteriophage MAC-1 DNA

Single-stranded DNA from MAC-1, a bacteriophage which specifically infects Bdellovibrio bacteriovorus, was used to investigate the transfection characteristics of Bdellovibrio. A very low efficiency of phage DNA uptake and expression [20 plaque-forming units (PFU) per μg DNA per 10⁸ viable cells] was shown to be independent of external parameters. DNase I resistance studies demonstrated that uptake of DNA occurred when the cells were heat-shocked and incubated at 30°C. The low efficiency of transfection was markedly enhanced by addition of dimethyl sulfoxide (DMSO); concentrations in the range of 28.5 to 31.0% (4.0 to 4.4 M) increased transfection 20- to 100-fold, corresponding to an average increase of 513-fold in transfection efficiency. Under these conditions, high efficiency transfection was dependent on exogenous Rb⁺ and Ca²⁺ but was inhibited by Mg²⁺ ion concentrations above 0.5 mM.