title: Biochemical studies of two Bacillus pumilus plasmids.
abstract: Bacillus pumilus NRS 576 harbored an estimated two copies per chromosome of a covalently closed, circular (CCC) deoxyribonucleic acid (DNA) molecule, the 576 plasmid. The 576 plasmid has a buoyant density of 1.698 g/cm(3) and a molecular weight of about 28 x 10(6). Plasmid copy number remained about the same in both exponentially growing and stationary-phase cells. Spontaneous variants of NRS 576 that formed spores at an elevated frequency were designated as W mutants. W mutants appeared to have lost the 576 plasmid on the basis of the following: W mutants (38 tested) lacked detectable CCC DNA, and the majority of the plasmid homologous sequences in bulk NRS 576 DNA were absent from bulk W mutant DNA. B. pumilus ATCC 7065 harbored at least 10 copies per chromosome of a CCC DNA element, the 7065 plasmid. The 7065 plasmid has a buoyant density of 1.696 g/cm(3) and a molecular weight of about 6 x 10(6). Although the copy number of the plasmid appeared to remain the same in exponentially growing and stationary-phase cells, an additional CCC form of higher molecular weight was detected in stationary-phase cells.
mesh_terms: D001407:Bacillus / Q000032:analysis* / Q000254:growth & development; D002250:Carbon Radioisotopes; D002499:Centrifugation, Density Gradient; D004269:DNA, Bacterial / Q000032:analysis*; D004270:DNA, Circular / Q000032:analysis*; D005111:Extrachromosomal Inheritance; D008854:Microscopy, Electron; D008970:Molecular Weight; D009153:Mutagens; D009154:Mutation; D009604:Nitrosoguanidines; D009693:Nucleic Acid Hybridization; D013171:Spores, Bacterial / Q000254:growth & development; D013936:Thymidine; D014316:Tritium
chemical_list: D002250:Carbon Radioisotopes; D004269:DNA, Bacterial; D004270:DNA, Circular; D009153:Mutagens; D009604:Nitrosoguanidines; D014316:Tritium; D013936:Thymidine