DEOXYRIBONUCLEIC ACID BASE COMPOSITION OF SPECIES OF KLEBSIELLA, AZOTOBACTER AND BACILLUS

Methods of molecular taxonomy were used to study the genome or deoxyribonucleic acid (DNA) of different strains of five genera of nitrogen-fixing bacteria. The DNA base compositions of all strains of Klebsiella pneumoniae (previously classified as strains of Achromobacter sp., Aerobacter aerogenes or K. pneumoniae) occupy a fairly narrow range of values from 56.7 to 62.5% G-C content. No significant difference was observed in the DNA base composition of bacteria which can fix molecular nitrogen and that of strains which do not fix nitrogen. Six strains of the species Azotobacter vinelandii and the one strain of A. chroococcum tested possess similar DNA base composition. The strain of Azotobacter agilis tested, however, had a DNA base composition different from these seven strains. The G-C content of the strains of Azotomonas insolita falls within the broad range of the Pseudomonas genus (55-70%), but the peritrichous flagellation of these strains eliminates them from this genus. Their classification still remains to be ascertained. Eleven strains of the species Bacillus polymyxa and B. macerans formed two homogenous groups of organisms with different DNA base composition. The atypical strain B. polymyxa Hino is genetically similar to the strains of the species Bacillus macerans and perhaps should be reclassified as such. © 1969 Swets & Zeitlinger.