DNA Base Composition and Homology Values in the Classification of Some Rhodococcus Species

Similar DNA homology values were recorded when a modified S1 nuclease technique and a standard nitrocellulose membrane filter method were applied to representative strains of Rhodococcus. The DNA homology data showed that R. globerulus, R. luteus and R. sputi form distinct genomic species. The congruence between the DNA homology and earlier numerical phenetic data was good, but there was evidence that some strains had been misclassified in the previous studies. In particular, the type strains of R. obuensis and R. sputi belong to a single genomic species. The former name is thus a later, subjective synonym of the latter. The guanine plus cytosine content of the DNA of the rhodococci fell within the range 61 to 72 mol%.