The actinomycete-genus Rhodococcus: a home for the "rhodochrous" complex

A numerical taxonomic classification study was carried out on 177 strains representing the "rhodochrous" complex and the genera Gordona, Mycobacterium and Nocardia. The strains were examined for 92 unit characters and the data were analysed by computer. Three clusters were defined at the 75 to 80% similarity level. The first was a heterogeneous cluster corresponding to the "rhodochrous" taxon whereas the other two contained Mycobacterium and Nocardia strains respectively. The good correlation between the numerical analysis and chemo-taxonomic, serological and genetical data collected from previous studies provides sufficient evidence for raising the "rhodochrous" taxon to generic status. We consider the generic name Rhodococcus Aopf to have priority over Proactinomyces (Jensen) Bradley & Bond, Jensenia Bisset & Moore and Gordona Tsukamura. In addition to the type species, Rhodococcus rhodochrous, nine species are recognized: R. bronchialis, R. coprophilus, R. corallinus, R. erythropolis, R. equi, R. rhodnii, R. rubrus, R. rubropertinctus and R. terrae.