Extrachromosomal elements in group N streptococci.
The deoxyribonucleic acid (DNA) of Streptococcus lactis C2, S. cremoris B(1), and S. diacetilactis 18-16 was labeled by growing cells in Trypticase soy broth containing (3)H-labeled thymine. The cells were gently lysed with lysozyme, ethylenediaminetetraacetic acid, and sodium lauryl sulfate. The chromosomal DNA was separated from plasmid DNA by precipitation with 1.0 M sodium chloride. The existence of covalently closed circular DNA in the three organisms was shown by cesium chloride-ethidium bromide equilibrium density gradient centrifugation of the cleared lysate material. In an attempt to correlate the loss of lactose metabolism with the loss of plasmid DNA, lactose-negative mutants of these organisms were examined for the presence of extrachromosomal particles. Covalently closed circular DNA was detected in the lactose-negative mutants of S. lactis C2 and S. diacetilactis 18-16. In S. cremoris B(1), however, no covalently closed circular DNA was observed by using cesium chloride-ethidium bromide gradients. Electron micrographs of the satellite band material from S. lactis C2 and its lactose-negative mutant confirmed the presence of plasmid DNA. Three distinct plasmids having approximate molecular weights of 1.3 x 10(6), 2.1 x 10(6), and 5.1 x 10(6) were observed in both organisms.
D002499:Centrifugation, Density Gradient; D004269:DNA, Bacterial / Q000032:analysis* / Q000302:isolation & purification; D004270:DNA, Circular / Q000032:analysis* / Q000302:isolation & purification; D004492:Edetic Acid; D005111:Extrachromosomal Inheritance; D013294:Lactococcus lactis / Q000032:analysis* / Q000378:metabolism; D007785:Lactose / Q000378:metabolism; D008854:Microscopy, Electron; D008970:Molecular Weight; D009113:Muramidase; D009154:Mutation; D012967:Sodium Dodecyl Sulfate; D013291:Streptococcus / Q000032:analysis* / Q000378:metabolism; D013941:Thymine; D014316:Tritium
D004269:DNA, Bacterial; D004270:DNA, Circular; D014316:Tritium; D012967:Sodium Dodecyl Sulfate; D004492:Edetic Acid; D009113:Muramidase; D007785:Lactose; D013941:Thymine