Symbiosis independent and symbiosis incompetent mutants of Bdellovibrio bacteriovorus 109J

Symbiosis independent (S(in)) mutants were isolated from the symbiosis dependent and symbiosis competent (S(d)comp⁺) B. bacteriovorus 109J. Independently isolated S(in) mutants were examined for their symbiosis competence and most were found to be comp⁺. Bdellovibrios comp^- were selected from the S(in)comp⁺ mutants. The S(in)comp⁺ bdellovibrios are always at a selective disadvantage, either against S(in)comp^- bdellovibrios (in organic medium) or against S(d)comp⁺ bdellovibrios (in buffer with Escherichia coli cells).