Ribosomal Ribonucleic Acid Cistron Similarities and Taxonomic Neighborhood of Brucella and CDC Group Vd

Abstract

Hybridizations were performed between labeled ribosomal ribonucleic acids from Brucella abortus ATCC 23448T(T = type strain) and from several other organisms on the one hand and deoxyribonucleic acids from type and representative Brucella strains and from many other gram-negative organisms on the other hand. Brucella forms a tight cluster, with deoxyribonucleic acid homologies close to 100%; its closest neighbors are CDC group Vd, followed by Phyllobacterium. This Brucella ribosomal ribonucleic acid branch links most closely at about 73.1°C Tm(e) with the Agrobacterium-Rhizobium cluster, which is itself a member of ribosomal ribonucleic acid superfamily IV. The deoxyribonucleic acid base compositions of Brucella strains range from 57.9 to 59.2 mol% guanine plus cytosine; the average genome molecular weights of the six species range from 2.37 × 109to 2.82 × 109.