Characterization by Electron Microscopy of Fused F-Prime Factors in
            <i>Escherichia coli</i>

Palchaudhuri, Sunil; Mazaitis, Anthony J.; Maas, Werner K.; Kleinschmidt, Albrecht K.

doi:10.1073/pnas.69.7.1873

Cited by 24 publications

(21 citation statements)

References 16 publications

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“…Furthermore, it is unlikely that fusion of plasmid DNA or deletions in the plasmid could have occurred in those double F' strains that had been randomly selected, as this would have been reflected as alterations in their sedimentation profiles. Fusion of F' plasmids in RecAstrains has been noted, but at frequencies much lower than those reported here (26).…”

Section: Resultscontrasting

confidence: 65%

dnaB gene of Escherichia coli K-12 affects superinfection inhibition between F' plasmids

Bezanson¹,

Iyer²

1975

J Bacteriol

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F' Escherichia coli K-12 strains bearing the chromosomal mutation dnaB43 offer significantly less resistance to the conjugational introduction of a second F' plasmid than do nonmutant strains. Both the entry exclusion and incompatibility components of superinfection inhibition are altered. This action of dnaB43 occurs regardless of the presence of a recA-minus mutation in matings in liquid cultures and on membrane filters and is not limited to a particular set of F' plasmids. These effects are co-transducible by phage P1 with the temperature sensitivity conferred by dnaB43. The effects also occur with a strain carrying dnaB107. In the double F' strains that arise, the two plasmids exist as units autonomous of one another and the chromosome.

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Section: Resultscontrasting

confidence: 65%

dnaB gene of Escherichia coli K-12 affects superinfection inhibition between F' plasmids

Bezanson¹,

Iyer²

1975

J Bacteriol

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“…Dissociated F-like R-factors showed a 9 x 101 to 15 x 10" da] which possesses a 0.56-mol fraction of G plus C (12,18,32). This plasmid type has been assumed (primarily by inference) to represent the drug resistance determinants of the R-plasmid (12,16,33). It seemed of some interest, therefore, to determine the mole fraction of G plus C possessed by the N-SuSm plasmid.…”

Section: Resultsmentioning

confidence: 99%

Molecular Nature of Two Nonconjugative Plasmids Carrying Drug Resistance Genes

1974

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SuSm and N-Tc, have been characterized. Both were of relatively small size (5 x 106 to 6 x 106 daltons) and present in multiple copies within their respective bacterial hosts. N-SuSm possessed a guanine plus cytosine content of 55%, whereas N-Tc was 49% guanine plus cytosine. Although these plasmids were inherently nontransmissible they could be mobilized by a large variety of transfer agents including Ent, Hly, and K88. The fih transfer factors tested were far more likely (about 200x) to mobilize these nonconjugative plasmids than were the fi+ transfer factors tested. Although the mobilization phenomenon was not found to be associated with a detectable level of direct stable recombinational union between N-SuSm or N-Tc with a transfer factor, we were able to demonstrate a low level of recombination between these replicons and a transfer factor by P1-mediated transduction. The isolation of recombinants between transfer factors and nonconjugative plasmids presumably represents one means by which unitary molecular types of R-plasmids arise and by which existing R-plasmids may acquire new resistance determinants.

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“…For instance, the buoyant density of the element is similar to that of the chromosomal DNA of the host. The molecular size of the 576 plasmid is about seven times that of a small E. coli plasmid, the ColEl factor (1,22), and nearly half the size of the F factor (11,20,27). An estimate of the number of copies of 576 plasmid per chromosome can be obtained by assuming that the molecular weight of the NRS576 chromosome is within the range of 2.5 x 109 to 5 x 109.…”

Section: Resultsmentioning

confidence: 99%

Plasmid in Bacillus pumilus and the Enhanced Sporulation of Plasmid-Negative Variants

Lovett

1973

J Bacteriol

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Approximately 3% of the deoxyribonucleic acid (DNA) of Bacillus pumilus NRS576 can be isolated as covalently closed, circular duplex molecules of homogeneous size. The mol wt of the 576 plasmid is approximately 30 million. NRS576 (plasmid+) is oligosporogenic; less than 1% of the cells form spores during incubation in liquid AK sporulation medium. Variants that form spores at a high frequency (greater than 50% spores in 24 h) occur spontaneously at a frequency of approximately 10'. More than 25 such variants have been examined and all lack detectable plasmid DNA. A relationship appears to exist between the oligosporogenic properties of NRS576 and the presence of the 576 plasmid.The existence of extrachromosomal genetic determinants (plasmids) is well documented for members of the Enterobacteriaceae, Staphylococcus aureus, and species of Pseudomonas (4,8,9,18). Those plasmids which have been mo §t extensively studied are characteristically small, covalently closed, circular duplex deoxyribonucleic acid (DNA) molecules which confer on the host known genetic functions. Examples of plasmid-directed host properties include the ability to conjugate, resistance to antibiotics and/or inorganic ions, and the production of colicins (18). Although most known plasmids were initially detected because of their genetic influence on the host, the development of biochemical techniques which permit the isolation of small, circular, duplex DNA molecules (21) has allowed the demonstration of plasmid-like mini-circle DNA in the absence of known genetic functions for the presumed extrachromosomal elements (5,12,19,23).Evidence for naturally occurring plasmids in sporeforming bacteria is presently limited to a study of the plasmid-like minicircular DNA isolated from Bacillus megaterium (3). Approximately 30 to 40% of the DNA of a strain of B. megaterium can be isolated as small, circular duplex molecules of sizes ranging from 0.8 to 34 ,um. These heterogeneous minicircles share extensive nucleotide sequence homology with the chromosomal DNA (Henneberry and Carlton, 1971, Bacteriol. Proc., p. 45; manuscript in preparation), and no genetic function has been attributed to them. It is presently unclear whether any of these heterogeneous minicircles are functionally analogous to plasmids, or whether they represent degraded and circularized chromosomal DNA.In the present report, evidence is presented which demonstrates that approximately 3% of the DNA of a strain of B. pumilus (a species related to B. subtilis [15][16][17]24]) can be isolated as circular duplex molecules of homogeneous size. Spontaneous variants that exhibit an increased frequency of sporulation lack detectable plasmid DNA.MATERIALS AND METHODS Bacteria. B. pumilus NRS576, obtained from R. E. Gordon, is sensitive to the transducing phage PBP1 (13) and does not exhibit the high rate of spontaneous mutation that is characteristic of a previously described strain of B. pumilus (14). In several experiments, two nitrosoguanidine-induced (16) auxotrophic derivatives of NRS576 were...

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Characterization by Electron Microscopy of Fused F-Prime Factors in Escherichia coli

Cited by 24 publications

References 16 publications

dnaB gene of Escherichia coli K-12 affects superinfection inhibition between F' plasmids

dnaB gene of Escherichia coli K-12 affects superinfection inhibition between F' plasmids

Molecular Nature of Two Nonconjugative Plasmids Carrying Drug Resistance Genes

Plasmid in Bacillus pumilus and the Enhanced Sporulation of Plasmid-Negative Variants

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