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Kinetics of recA function in conjugational recombinant formation

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Genetic recombination was studied in F- strains of E. coli carrying a mutation (recA200) that confers a thermosensitive Rec- phenotype. Recombination during Hfr matings at 35C was monitored by raising the temperature of incubation to 42C at various intervals so that only merozygotes that had completed those functions dependent on the activity of the recA gene product could form recombinant progeny. The results indicated that no more than 1–2% of the merozygotes present while mating was in progress were able to form recombinant colonies at 42C. Separation of mating pairs reduced the yield of recombinants obtained at 35C by 50 to 200-fold if plating on agar medium was delayed for 15–30min by continuing incubation in broth medium. recA200 merozygotes that were also recB21 sbcB15 proved relatively stable when plating was delayed in this manner, which suggested that Hfr DNA is prone to exonuclease inactivation in recA200 merozygotes after mating pairs have separated. Post-mating incubation in high salt medium or on agar plates promoted the recovery of recombinants at 35C. However, the majority of recA200 merozygotes did not acquire the ability to form recombinant colonies at 42C under these more stable conditions until mating pairs had been separated and incubation continued at 35C for 40–60 min. It was concluded that recA200 strains are partially defective for recombination even at low temperature but that terminating mating promotes the recovery of recombinants. A mechanism involving the stimulation of RecA activity by mating pair separation is postulated to account for the efficient recovery of recombinants from HfrxF- recA200 crosses at 35C.

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  1. Bachmann, B.J.: Pedigrees of some mutant strains of Escherichia coli K-12. Bacteriol. Rev. 36, 525–557 (1972)

  2. Bachmann, B.J., Low, K.B., Taylor, A.L.: Recalibrated linkage map of Escherichia coli K-12. Bacteriol. Rev. 40, 116–167 (1976)

  3. Birge, E.A., Low, K.B.: Detection of transcribable recombination products following conjugation in Rec+, RecB- and RecC- strains of Escherichia coli K-12. J. Mol. Biol. 83, 447–457 (1974)

  4. Castellazzi, M., Morand, P., George, J., Buttin, G.: Prophage induction and cell division in E. coli. V. Dominance and complementation analysis in partial diploids with pleitropic mutations (tif, recA, zab and lexB) at the recA locus. Mol. Gen. Genet. 153, 297–310 (1977)

  5. Clark, A. J.: Recombination deficient mutants of E. coli and other bacteria. Annu. Rev. Genet. 7, 67–86 (1973)

  6. Curtiss, R., Charamella, L.J., Stallions, D.R., Mays, J.A.: Parental functions during conjugation in Escherichia coli. Bacteriol. Rev. 32, 320–348 (1968)

  7. Demerec, M., Adelberg, E.A., Clark, A.J., Hartman, P.E.: A proposal for a uniform nomenclature in bacterial genetics. Genetics 54, 61–74 (1966)

  8. Emmerson, P.T., West, S.C.: Identification of protein X of Escherichia coli as the recA + /tif + gene product. Mol. Gen. Genet. 155, 77–85 (1977)

  9. Gudas, L.J., Mount, D.W.: Identification of the recA(tif) gene product of Escherichia coli. Proc. Natl. Acad. Sci. U.S.A. 74, 5280–5284 (1977)

  10. Gudas, L.J., Pardee, A.B.: A model for the regulation of E. coli DNA repair functions. Proc. Natl. Acad. Sci. U.S.A. 72, 2330–2334 (1975)

  11. Guyer, M.S., Clark, A.J.: cisDominant, transfer-deficient mutants of the Escherichia coli K-12 F sex factor. J. Bact. 125, 233–247 (1976)

  12. Holloman, W.K., Wiegand, R., Hoessli, C., Radding, C.M.: Uptake of homologous single-stranded fragments of superhelical DNA: A possible mechanism for initiation of genetic recombination. Proc. Natl. Acad. Sci. U.S.A. 72, 2394–2398 (1975)

  13. Itoh, T., Tomizawa, J.: Inactivation of chromosomal fragments transferred from Hfr strains. Genetics 68, 1–11 (1971)

  14. Kushner, S.R., Nagaishi, H., Clark, A.J.: Indirect suppression of recB and recC mutations by exonuclease I deficiency. Proc. Natl. Acad. Sci. U.S.A. 69, 1366–1370 (1972)

  15. Lloyd, R.G.: The segregation of the SbcA and Rac phenotypes in an Escherichia coli recB - mutant. Mol. Gen. Genet. 134, 249–259 (1974)

  16. Lloyd, R.G.: Hyper-recombination in Escherichia coli K-12 mutants constitutive for protein X synthesis. J. Bact. 134, 929–935 (1978)

  17. Lloyd, R.G., Barbour, S.D.: The genetic location of the sbcA gene of Escherichia coli. Mol. Gen. Genet. 134, 157–171 (1974)

  18. Lloyd, R.G., Low, B.: Some genetic consequences of changes in the level of recA gene function in Escherichia coli K-12. Genetics 84, 675–695 (1976)

  19. Lloyd, R.G., Low, B., Godson, G.N., Birge, E.A.: Isolation and characterisation of an Escherichia coli K-12 mutant with a temperature-sensitive RecA- phenotype. J. Bact. 120, 407–415 (1974)

  20. Low, K.B.: Formation of merodiploids in matings with a class of Rec- recipient strains of Escherichia coli K-12. Proc. Natl. Acad. Sci. U.S.A. 60, 160–167 (1968)

  21. Low, K.B.: Rapid mapping of conditional and auxotropic mutations in Escherichia coli K-12. J. Bact. 113, 798–812 (1973a)

  22. Low, K.B.: Restoration by the rac locus of recombinant forming ability in recB -and recC - merozygotes of Escherichia coli K-12. Mol. Gen. Genet. 122, 119–130 (1973b)

  23. Low, K.B., Wood, T.H.: A quick and efficient method for interruption of bacterial conjugation. Genet. Res. Camb. 6, 300–303 (1965)

  24. Luria, S.E., Burrous, J.W.: Hybridisation between Escherichia coli and Shigella. J. Bact. 74, 461–476 (1957)

  25. McEntee, K.: Protein X is the product of the recA gene of Escherichia coli. Proc. Natl. Acad. Sci. U.S.A. 74, 5275–5279 (1977)

  26. Morand, P., Blanco, M., Devoret, R.: Characterisation of lexB mutations in Escherichia coli K-12. J. Bact. 131, 572–582 (1977)

  27. Morand, P., Goze, A., Devoret, R.: Complementation pattern of lexB and recA mutations in Escherichia coli K12: mapping of tif-1, lexB and recA mutations. Mol. Gen. Genet. 157, 69–82 (1977)

  28. Paul, A.V., Riley, M.: Joint molecule formation following conjugation in wild type and mutant Escherichia coli recipients. J. Mol. Biol. 82, 35–56 (1974)

  29. Riley, M., Pardee, A.B.: Nutritional effects on frequencies of bacterial conjugation. J. Bact. 83, 1332–1335 (1962)

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Correspondence to Robert G. Lloyd.

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Communicated by A.J. Clark

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Lloyd, R.G., Johnson, S. Kinetics of recA function in conjugational recombinant formation. Molec. Gen. Genet. 169, 219–228 (1979).

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  • Agar
  • Recombination
  • Agar Plate
  • Agar Medium
  • High Salt