Abstract
THE average content of DNA in Bacillus spores is unaffected by the growth medium and is constant for each species1. Within the Bacillus group, however, the average amount of DNA per spore varies from species to species1. A cell of B. cereus contains on average twice as much DNA as the spore and during sporulation this DNA is divided equally between the spore and the sporangium2. Estimates3–5 of genome size vary from 1.3 × 109 to 10 × 109 daltons and the number of genomes per cell from 2 to 44–8. Some of these variations may be associated with differences within the cells rather than differences of methodolqgy; spores within a population vary not only in size and shape, but also in their content of stainable chromatin9. Moreover, in ‘Renografm’ density gradients10, spores band within a range of densities. If spores are taken from a narrow part of this range, regrown and rebanded, the original pattern of dispersal occurs, suggesting that spores in the same population normally show variation in density as well as in size (A. I. Aronson, personal communication).
Published Version
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