Deoxyribonucleic Acid Reassociation in the Classification of the 'rhodochrous' Complex and Allied Taxa

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Abstract
The degree of binding was determined between DNA preparations from gordonae and rhodochrous strains and uracil-labeled DNA from 5 reference strains, Nocardia asteroides NK20, N. pellegrino P11, Gordona bronchialis T1, G. terrae T5 and rhodochrous strain R90. Most of the rhodochrous and pellegrino strains fell into 1 of 2 genetically homogeneous taxa. The nucleotide sequence homology data also suggested that G. bronchialis, G. rubra and more equivocally G. terrae, formed distinct species. The values for DNA relatedness between these species and between them and the rhodochrous homology groups, were comparatively low. Only a small degree of nucleotide sequence homology was found between the N. asteroides reference system and the rest of the taxa studied. The nucleotide composition of the DNA preparations from 29 of the 30 test strains fell between 63-69 mol % guanine plus cytosine.