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At least 19 recordsLinked to original sources
PubMed1966

Loss and repair of conjugal fertility and infectivity of the resistance factor and sex factor in Escherichia coli.

Hirota, Yukinori (University of Osaka, Osaka, Japan), Toshio Fujii, and Yukinobu Nishimura. Loss and repair of conjugal fertility and infectivity of the resistance factor and sex factor in Escherichia coli. J. Bacteriol. 91:1298-1304. 1966.-The drug-resistance factor, R, and the sex factor, F, have homologous traits, including contagious transmission, mediation of sexuality of the host cell, and autonomous replication in their host bacteria. Cooperation between F and R factors was found with a mutant R factor, which is nontransmissible in F(-) bacteria, becoming transmissible when introduced into bacteria carrying F. Conversely, the chromosome of a sterile male strain carrying the mutant sex factor, F(r), becomes transmissible when an R factor is introduced into the cell. The genetic determinants of R factors have been analyzed by isolation of mutant R factors, by sexual conjugation of the host bacteria, and by transduction of R factors with phage P1kc. The fertility determinant of the R factor, m, is inseparable from the determinant for its infectivity, but can be separated from the loci for autonomous replication of the R factor. R and F thus carry genetic determinants governing the same functions.

Acridines↗
PubMed1976

R factor variants with enhanced sex factor activity in Pseudomonas aeruginosa.

The R factor R68 readily promotes chromosome transfer in Pseudomonas aeruginosa strain PAT, but shows little such sex factor activity in strain PAO. A variant of this plasmid, R68.45, has been isolated which produces recombinants in PAO plate matings at frequencies of 10(-3)--10(-5) per donor cell for markers in the 0-60 min region of the chromosome. Little or nor chromosome transfer was shown in liquid media. The kinetics of chromosome transfer were studied by interrupting matings on solid media with nalidixic acid. Five chromosomal markers, mapping in widely spaced regions of the chromosome all entered 3-5 min after initiation of mating. These results, combined with linkage studies, indicated that R68.45, unlike the Pseudomonas sex factors FP2 and FP39, promotes chromosome transfer from a range of origin sites and can thus be used for mapping the region of the P. aeruginosa chromosome later than 40 min. R68.45 and other similar variants were isolated from rare chromosomal recombinants appearing in crosses between PAO(R68) donors and PAO recipients in which selection for ARGB+ was made. Selection for other chromosomal markers did not result in such variants suggesting that plasmides of the R68.45 type arise by recombination of genetic material between the R68 plasmid and certain regions of the bacterial chromosome.

Chromosome Mapping↗
PubMed1975

[The influence of differences in the Rec-genotype of E. coli cells on the function of sex factor F'].

Functions of the sex factor F' depended not only on damage of the genes, controlling the recombination capacity of bacterial cells, but also on suppression of the rec-gene mutations. Suppression of mutations of these genes was accompanied by the capacity of the sex factor to mobilize the chromosome for the transfer from the rec-bacterial cells. If it were demonstrated that the cells of the Jc 9604-131 strain actually carried the inverse mutation of the rec A gene, this would prove that these mutations resulted in the restoration of a recombination possibility between the sex factor F' and the bacterial chromosome.

Escherichia coli↗
PubMed1972

Self-transfer and genetic recombination mediated by P, the sex factor of Vibrio cholerae.

Vibrio cholerae cells, infected with the sex factor P, produce discrete, plaque-like clearings when plated on lawns of P(-) cells. We investigated the nature of these clearings and conclude that they are probably sites of active mating. We developed a quantitative assay for P(+) cells and used it to study the kinetics of sex factor spread in broth cultures. Both established and newly infected donor populations were efficient sex factor donors, indicating that P is not self-repressed. We also investigated the kinetics of recombinant formation in broth matings. In 1-hr matings, we routinely found recombination frequencies of 10(-6) per donor cell. Kinetic studies of recombinant formation showed that the markers tested all appeared at early times. Thus P, the V. cholerae sex factor, seems to resemble F in its transfer properties.

Agar↗
PubMed1962

Transduction of the attached sex factor of Escherichia coli.

DeWitt, Susanne K. (University of California, Berkeley) and Edward A. Adelberg. Transduction of the attached sex factor of Escherichia coli. J. Bacteriol. 83:673-678. 1962.-The linkage of the sex factor to one extremity of the chromosome in Hfr cells of Escherichia coli has been confirmed by transduction experiments. In Hfr P4x-6, lac is the last marker to penetrate the female during conjugation. When lac(+) was transduced from P4x-6 into a lac(-) strain by phage Plkc, 5% cotransduction of the sex factor was observed. No cotransduction of the sex factor was observed when markers other than lac(+) were selected.The transduced males resembled the Hfr parent with respect to the site of attachment and orientation of the sex factor, the order of genetic markers transferred, and the gradient of recombination frequencies produced with a given female. When the lac(-) recipient used in the transduction carried an sfa locus in a different region of the chromosome, the over-all rate of cotransduction was tenfold lower, but the transduced males again resembled the Hfr parent in their sexual behavior.

Chromosomes↗
PubMed1972

Conjugation in Escherichia coli: failure to confirm the transfer of part of sex factor at the leading end of the donor chromosome.

Experiments were carried out attempting to determine whether part of sex factor is transferred at the leading end of the Hfr chromosome during conjugation. In the first experiment, an analysis was made of the donor properties of recombinant strains which had inherited the terminal but not the proximal marker from an Hfr. Secondly, recombinants integrating an extremely proximal marker from an Hfr were examined for the inheritance of a sex factor affinity locus adjacent to this marker. In the third experiment, proximal transfer of the wild-type allele of a temperature-sensitive sex factor mutation was looked for, using as recipient a temperature-sensitive Hfr strain, and as donor a wild-type Hfr isogenic with respect to the site of sex factor integration. In none of these experiments could the presence of sex factor material at the leading end be demonstrated. The results do not rule out the possibility that part of F is transferred proximally but only integrated at a very low frequency. They do, however, conflict with certain findings of other authors which, in the past, have been taken as evidence for the transfer of part of F at the leading end.

Alleles↗
PubMed1980

Recombination genes on the Escherichia coli sex factor specific for transposable elements.

The Escherichia coli sex factor stimulates precise excision of transposons Tn5 and Tn10 from sites either within the bacterial chromosome or within the factor itself. We have isolated two kinds of mutations that affect this activity. The ferA mutations eliminate the stimulation; the ferB mutations enhance it in the presence of FerA+. We conclude that ferA defines a sex factor gene that stimulates precise excision. The ferB mutations also specifically increase the rate of recombination between two IS3 elements on F' lac-pro (F'128) in a reaction that requires the product of recA. The stimulation of this recombination by ferB also requires an active ferA gene, which implies that the ferA gene stimulates this reaction as well as precise excision. A ferA mutation was mapped at 84.2 kilobases on the F factor, and a ferB mutation was mapped at 82.5 kilobases. The fer mutants were obtained by an approach that permits the isolation of mutants affecting precise excision.

Chromosome Mapping↗
PubMed1982

Cleavage of lambda repressor and synthesis of RecA protein induced by transferred UV-damaged F sex factor.

Transfer of a UV-damaged F sex factor to a recipient lambda lysogen induces prophage lambda development. Under these conditions RecA protein synthesis was induced and lambda repressor cleaved, as observed upon direct induction, that is, when the recipient lambda lysogen was directly exposed to UV-light. The efficiency of induction of RecA protein synthesis in recipient bacteria which had received an irradiated F-lac factor was about 80% of that measured upon direct induction. We observed the simultaneous disappearance of lambda repressor and a slight production of cleavage fragments; quantitation by densitometric scanning of the autoradiogram after correction for the efficiency of transfer indicated that 55% of lambda repressor was cleaved. Transfer of UV-damaged Hfr DNA failed to induce RecA protein synthesis. A lambda phage vector carrying oriF, the cloned origin of F plasmid replication, after exposure to UV-light and infection of a recipient lysogen, induced RecA protein synthesis and a moderate but significant cleavage of lambda repressor. Indirect induction by UV-damaged F sex factor or phage lambda oriF resulted in biochemical cellular reactions similar to those observed upon direct induction. LexA repressor that negatively controls RecA protein synthesis appeared more susceptible to cleavage than did lambda repressor.

Bacterial Proteins↗
PubMed1970

Segregation of functional sex factor into minicells.

The segregation of a bacterial plasmid, the sex factor F', has been investigated in a cell-division mutant of Escherichia coli which produces small anucleate cells (minicells). Significant amounts of isotopically labeled DNA segregate into minicells dependent upon the presence of F'. Minicells containing F'Gal or F'(lambda) are shown to donate the plasmid in conjugation. These results demonstrate that the sex factor may be dissociated from the bacterial chromosome and that this separation does not prevent its subsequent transfer.

Carbon Isotopes↗
PubMed1965

EFFECT OF INTEGRATED SEX FACTOR ON TRANSDUCTION OF CHROMOSOMAL GENES IN ESCHERICHIA COLI.

Pittard, James (Yale University, New Haven, Conn.). Effect of integrated sex factor on the transduction of chromosomal genes in Escherichia coli. J. Bacteriol. 89:680-686. 1965.-Generalized transducing phage P1kc can contransduce the markers tna and ilv in Escherichia coli K-12 at a frequency of approximately 25%. When sex factor is integrated into the donor chromosome between tna and ilv, as in Hfr AB313, the entire sequence tna F ilv is not cotransduced at a detectable frequency, nor is F cotransduced with either tna or ilv. The frequency with which ilv is transduced from Hfr AB313 to female recipients is approximately one-eighth the frequency obtained when either F(+) or female strains are used as donors. This reduction of transduction frequency does not occur if the recipient is an Hfr male similar to AB313. The reduction is attributed to pairing difficulties which occur when the transduced fragment carrying the ilv genes also carries sex-factor material. When ilv(+) is transduced from a female to an ilv(-) derivative of AB313, 70% of the transductants are converted to F(+) males. A model is proposed to account for all of these observations.

Chromosomes↗