Analysis of phenotypic diversity among host-independent mutants of Bdellovibrio bacteriovorus 109J

Host-independent (H-I) mutants of the obligate bacterial parasite Bdellovib rio bacteriovorus were isolated from wild-type strain 109J. Seven H-I mutan ts differed in morphological features such as cell length (2-30 mum) and sh ape (short or long spirals or rod-like), plaque size, and pigmentation (fro m almost colorless to bright orange). The mutants exhibited widely differen t growth capabilities in rich medium, with biomass doubling times and final biomass varying by a factor of two or more. Growth was always enhanced by the addition of host cell extract or divalent cations to the growth medium, but the effect varied widely between the mutants. Analysis of the hit regi on, mutations in which were previously proposed to be associated with the H -I phenotype, revealed that changes in the nucleotide sequence in this regi on occurred only in three of the seven mutants.