Deoxyribonucleic acid characterization of Bdellovibrios.

The guanine plus cytosine (GC) content of the deoxyribonucleic acid (DNA) of 11 isolates of host-dependent (H-D) bdellovibrios and 18 host-independent (H-I) derivatives was determined from thermal denaturation curves and buoyant densities in CsCl. The H-D and respective H-I cultures have GC contents which are identical within the limits of experimental error. Most cultures of Bdellovibrio bacteriovorus, including the holotype culture, have 50.4 +/- 0.9 moles% GC in their DNA; two bdellovibrio isolates of presently uncertain nomenclatural status contain DNA of about 43% GC. Optical melting profiles of all the DNA from all of these organisms are particularly steep, indicating little compositional heterogeneity. Chromatography of acid hydrolysates of Bdellovibrio nucleic acids reveal no unusual components. The DNA content per cell of one H-I derivative is about one-third the amount per Escherichia coli cell growing at a comparable rate.