Folded chromosomes of vegetative Bacillus subtilis: composition and properties.

The isolation of folded DNA from Bacillus subtilis, a Gram positive bacterium is described. When the lysis was achieved with 1 M NaCl a slow sedimenting nucleoid was obtained (1600-2000 S). Conversely, when the lysis was achieved with 0.2 M NaCl a fast sedimenting nucleoid was obtained (3500-4000 S). The yield of folded DNA was between 80 to 90 % of the total lysate DNA. Both nucleoids contained the same amount of RNA, but the relative proportions of lipids and proteins were different. Folded chromosomes were prepared in the presence of spermidine: artifactual protein binding is shown to be unlikely. Electrophoresis of nucleoid proteins showed a dominant polypeptide (MW = 36,000), which remained associated with DNA after sarcosyl treatment and could be partially removed by heat mediated DNA unfolding. In vitro transcription by endogenous RNA polymerase bound to the fast sedimenting-nucleoid was rifamycin resistant; the template capacity of the fast sedimenting-nucleoid was compared with that of the completely unfolded chromosomes.