Membrane Association of Conjugally Transferred Deoxyribonucleic Acid in
            <i>Escherichia coli</i>
            Minicells

Shull, F. W.; Fralick, Joe A.; Stratton, Lewis P.; Fisher, William D.

doi:10.1128/jb.106.2.626-633.1971

Cited by 24 publications

(7 citation statements)

References 38 publications

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“…By using X rays to introduce double-strand breaks in DNA, Burrell et al (5) concluded that the chromosome of Micrococcus radiodurans has one or two membrane attachment points. Shull et al (35) reported that episomal DNA introduced conjugally into E. coli minicells is attached to the membrane at many points.…”

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confidence: 99%

Effect of Rifampin on the Structure and Membrane Attachment of the Nucleoid of Escherichia coli

1973

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Deoxyribonucleic acid (DNA) of Escherichia coli was found to be attached to the cell membrane at about 20 points. This was determined by fractionation of X-irradiated cells with the M band (magnesium-Sarkosyl crystals) technique. The number of attachment points was computed from the relationship between the amount of DNA in M bands and the number of double-strand breaks introduced by the X-ray treatment. The number of attachment points was decreased fourfold by treatment of cells with rifampin. This effect was apparently due to the action of the drug on ribonucleic acid (RNA) polymerase since the drug did not affect a mutant whose RNA polymerase is resistant to rifampin. This suggests that there may be two classes of attachment points of DNA on the membrane, some of which are removed by rifampin treatment and some which are not. Rifampin treatment also resulted in the uncondensing of isolated nucleoids and in an axial appearance of the nucleoids in ultrathin sections. The results suggest that RNA polymerase plays a role, direct or indirect, in maintaining the structure of the bacterial nucleoid and in some of its attachment to the membrane.

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confidence: 99%

Effect of Rifampin on the Structure and Membrane Attachment of the Nucleoid of Escherichia coli

1973

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“…An analysis of the molecular weights of DNA transferred to Eex+ and to Eexrecipients was undertaken to investigate this possibility. Shull et al (27) have reported that DNA transferred from Hfr donors to F-minicells has a weightaverage molecular weight of 20 x 106 to 30 x 10! We measured the molecular weights of DNA transferred from Hfr and R+ donors to excluding and nonexcluding minicell recipients.…”

Section: Resultsmentioning

confidence: 99%

Molecular Studies on Entry Exclusion in Escherichia coli Minicells

1972

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Minicells produced by abnormal cell division in a strain of Escherichia coli (K-12) have been employed here to investigate the phenomenon of "entry exclusion." When purified minicells from strains containing F' or R factors, or both, are mated with radioactive thymidine-labeled Hfr or R+ donors, the recipient minicells can be conveniently separated from normal-sized donors following mating, and the products of conjugation can be analyzed in the absence of donors and of further growth of the recipients. Transmissible plasmids or episomes are transferred less efficiently to purified minicells derived from strains carrying similar or related elements than to strains without them. Measurement of deoxyribonucleic acid (DNA) degradation and determination of weight-average molecular weights following transfer indicate that degradation of transferred DNA or transfer of smaller pieces cannot account for the comparative reduction in transfer to entry-excluding recipients. Therefore, we conclude that entry exclusion operates to prevent the physical entry of DNA into recipients expressing the exclusion phenotype. The R-produced repressor (product of the drd+ gene), which represses fertility (i.e., ability to act as donor), reduces exclusion mediated by R or F factor, or both, in matings between strains carrying homologous elements. Furthermore, the data suggest that the presence of the F pilus or F-like R pilus on recipient cells ensures maximum expression of the exclusion phenotype but is not essential for its expression. In contrast to previous suggestions, we found no evidence for a reduction of entry exclusion attributable to the DNA temperature-sensitive chromosomal mutation dnaB(TS).In 1958 Lederberg observed that conjugal matings between two F + strains were less efficient than matings between an F+ strain and a strain that did not harbor an F fertility factor. Currently it is accepted that transmissible plasmids or episomes usually are transferred less efficiently to strains that carry similar or related elements, suggesting that a determinant linked to the sex factor confers on the cell immunity against conjugal infection by an isogenic or closely related sex factor. Novick (23) has suggested that this immunity is the result of two distinct effects, "entry exclusion" and "plasmid incompatibility."Incompatibility is considered to be operative after deoxyribonucleic acid (DNA) enters the recipient cell and is evidenced by the segregation of the newly transferred plasmid out of the population. It has been postulated that the failure of the incoming plasmid to replicate normally and its subsequent loss reflect a lack of available attachment sites (16). The occupa-tion of a maintenance site(s) by the resident plasmid presumably blocks the attachment of a similar or isogenic plasmid. However, the maintenance site model does not explain all cases of incompatibility (see Novick [23] for detailed discussion).On the other hand, it has been suggested that entry exclusion imposes a barrier to the physical transfer of DNA betwee...

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“…Conflicting evidence of "membrane-attachment" has been reported using a different method of preparation (the M' band method [226]-by direct lysis of lysozyme-EDTA spheroplasts with Sarkosyl on sucrose gradients. DNA in minicells derived from an R factor, or from F ColV ColB trp cys (neither plasmid investigated in "cleared lysates") or from an F+ parent was concluded to be membrane associated from its co-sedimentation with the M band (213).…”

Section: Discussionmentioning

confidence: 99%