Deoxyribonucleic Acid Base Compositions among Thermophilic Actinomycetes: the Occurrence of two Strains with Low GC Content

Abstract

SUMMARY: Deoxyribonucleic acid (DNA) was extracted from two strains of Thermomonospora, two strains of Thermoactinopolyspora and one thermophilic strain of Streptosporangium. Base compositions were determined from ‘melting-temperatures’ (Tm) and, in two cases, from buoyant density. DNAs from both Thermoactinopolyspora strains and one Thermomonospora strain were of similar base composition to those previously reported for mesophilic actinomycetes. The other Thermomonospora strain and the Streptosporangium strain, both of which had higher temperature requirements and tolerance for growth, possessed DNA of lower GC content. These findings are discussed in relation to phylogeny, thermophily and the universality of the genetic code.