Taxonomy of Bacillus circulans Jordan 1890: Base Composition and Reassociation of Deoxyribonucleic Acid

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Abstract
The guanine-plus-cytosine (G + C) contents of 123 strains previously identified as B. circulans JOrdan 1890 were determined. Of the strains examined, only 18 had G + C contents of 37-41 mol%, a range that included the G + C content (38.1 mol%) of the type strain. A major portion of the strain (93 strains) had G + C contents in the range from 46-55 mol%. For 7 strains the G + C contents ranged from 42-45 mol% and for another small group of 5 strains the G + C contents ranged from 56-61 mol%. DNA reassociation studies revealed that 10 of the 18 strains with G + C contents of 37-41 mol% were closely related genetically to each other and to the type strain. This genetically related group was phenotypically quite homogeneous. Most of the strains were probably misclassified as B. circulans. The phenotypic heterogeneity of the species B. circulans Jordan 1890 was not due to inherent variability of genetically related strains, but to variability introduced by inclusion of genetically unrelated organisms.

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