A Further Numerical Taxonomic Study of the Rhodochrous Group

ABSTRACT A computer taxonomy was carried out as an aid to clarify the relationships between the genera Mycobacterium , and Nocardia as well as the ‘Rhodochrous’ group. The last group contained slightly acid‐fast organisms isolated from sputa and soil and also included strains received as “ Mycobacterium rhodochrous .” The group had been proposed as the genus Gordona by the present author. The rhodochrous group formed a cluster at the 87% similarity level and was clearly separated from all strains of the genera Mycobacterium and Nocardia . The cluster of the rhodochrous group was divided into seven subclusters at the 90% similarity level, and six of the seven corresponded to six species of the genus Gordona: G. bronchialis; G. rubropertincta (synonym G. rubra ); G. terrae; G. aurantiaca; G. rhodochroa; G. rosea . If one accepts the concept that a phenetically well‐defined cluster is a species, each of the subclusters of the rhodochrous group should be regarded as a species and the entire group as a genus. Discrepancies between the results of numerical classification and the results of lipid analyses remain as a problem to be solved in the future.