Heterogeneity of deoxyribonucleic acid molecules isolated from Mycobacterium smegmatis

M. V. Norgard, T. Imaeda

Research output: Contribution to journalArticlepeer-review


Bulk chromosomal deoxyribonucleic acids (DNAs) of M. smegmatis strains 607+ (wild type) and 607-1 (Str(r)) and orange-red pigmented variants (OR) were separated into two distinct bands (types 1 and 2) by cesium chloride density gradient centrifugation. Thermal denaturation analyses showed that type 1 and 2 DNA fragments of these strains possessed quanine plus cytosine contents averaging 69.2% and 60.8%, respectively. Type 1 and 2 DNAs from all strains tested were recovered in relatively equal quantities upon isolation and were found to have similar molecular weights (3.0x107). Spectrophotometric assay of DNA reassociation showed that homology between any type 1 and 2 DNA fragments was always very low (29 to 33%), even within the same strain. Homologies among type 1 DNAs isolated from any strain were always high (92 to 98%), whereas homologies between type 2 DNA isolated from OR strains and that from their parental strain 607-1 were lower (51 to 55%). Transformation experiments revealed that methionine, leucine, folic acid, and streptomycin markers were found exclusively in type 1 DNA fragments. In addition to the two types of chromosomal DNA, plasmid DNA possessing a molecular weight of about 4x106 was found in strain 607-1.

Original languageEnglish (US)
Pages (from-to)766-771
Number of pages6
JournalJournal of Bacteriology
Issue number2
StatePublished - Dec 1 1980

ASJC Scopus subject areas

  • Microbiology
  • Molecular Biology


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