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 acidfast 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.