Deoxyribonucleic Acid Homologies and Ribosomal Ribonucleic Acid Similarities Among Sporeforming Members of the Order Actinomycetales

Abstract
We investigated the relatedness of 24 named species belonging to 18 sporeforming genera of the order Actinomycetales with respect to deoxyribonucleic acid-deoxyribonucleic acid homology and ribosomal ribonucleic acid cistron similarity. A total of 21 of these species grouped in three deoxyribonucleic acid homology clusters in which the homology values ranged between 20 and 45%. The first cluster contained Actinoplanes, Ampullariella, Amorphosporangium, Micromonospora, and Dactylosporangium; the second cluster contained Streptosporangium, Planomonospora, and Planobispora; and the third cluster included Streptomyces, Chainia, Kitasatoa, Streptoverticillium, Microellobosporia, Ely-trosporangium, and Actinosporangium. The close molecular genetic relationship of the organisms in each cluster was supported by several physiological and biochemical properties of taxonomic value. The ribosomal ribonucleic acid cistron similarity data did not indicate that any two of these clusters were specifically related to each other. Microtetraspora viridis DSM 43175, Spirillospora albida DSM 43034, and Actinomadura madurae DSM 43067 grouped separately from all of the the other organisms investigated.