SUMMARY: Eight strains of Gordona aurantiaca, 89 representatives of the genera Mycobacterium, Nocardia and Rhodococcus and a single strain of Brevibacterium linens were the subject of numerical phenetic analyses using 92 unit characters. The G. aurantiaca cluster was robust in different numerical analyses and equivalent in rank to the genera Mycobacterium, Nocardia and Rhodococcus. The presence of a characteristic mycolic acid and completely unsaturated menaquinones distinguished G. aurantiaca strains from mycobacteria, nocardiae and rhodococci. The congruence between the numerical and phenetic data indicate that G. aurantiaca strains form a distinct taxon resembling other mycolic acid-containing taxa in wall, fatty acid and polar lipid composition. Since the genus Gordona is no longer valid, a new niche is needed for G. aurantiaca.
