SIMILARITY IN DNA OF VARIOUS MORPHOLOGICALLY DISTINCT ACTINOMYCETES

Abstract

The DNA base composition and degree of homology of Streptomyces griseus DNA of various morphologically distinct actinomycetes were studied to determine any genotypic difference between their DNA. The average percentage of guanosine-cybosine (GC), analyzed by the paper chromatographic method was in the range of 67.5-74.5 and generally between 70 and 74 if Nocardia and its relatives were expected; the difference was gradual and failed to delineate any organisms. Organisms having the nocardial type of cell wall (Nocardia and Micropolyspora), occupied the lower region followed by Streptosporangium and Microellobosporia. The DNA homology test by the DNA-agar method showed that no conspicuous difference applicable to the classification was recognizable inter- and intragenerically even when strains of Myco-bacterium and Thermoactinomyces were included as compared with the marked difference of Escherichia coli used as a control. A possible phylogenetic position of various mesophilic actinomycetes is presented.