- Volume 43, Issue 2, 1966

The base compositions of deoxyribonucleic acids extracted from aerobic pseudomonads were determined by examination of the buoyant density of each sample in caesium chloride (CsCl) gradients. A collection of 165 strains, representing many of the principal biotypes among aerobic pseudomonads, was subjected to this examination. The similarities and differences in the base compositions of the genetic material have been compared with the taxonomic arrangements suggested by the comparison of phenotypic (largely nutritional and enzymic) features. The data on base composition of the deoxyribonucleic acids of the various cultures support, for the greater part, the conclusions of Stanier, Palleroni & Doudoroff (1966) and of Redfearn, Palleroni & Stanier (1966). Data are also presented on pseudomonads not included in the latter studies.

A comparative study of many strains of Pseudom,onas pseudomallei and Bacillus mallei has shown that these two species are very similar with respect to their nutritional and biochemical properties, thus confirming earlier claims of a relationship between them, based on such criteria as pathological and serological properties. P. pseudomallei is in all respects a typical and nutritionally highly versatile member of the genus Pseudomonas. In view of this fact we propose that B. mallei should also be placed in the genus Pseudomonas, even though it is a permanently non-motile bacterium. The ecology and possible evolutionary relationships between the two species are discussed in the light of the present findings.