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Biophysical Journal 9: 391-420 (1969)
© 1969 the Biophysical Society

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Conjugation in Escherichia coli K-12 and Its Modification by Irradiation

Thomas H. Wood and Roger H. Walmsley

ABSTRACT

The steps of normal bacterial conjugation (union, transfer, integration and segregation) are described in analytical terms. Only two parameters are utilized: {nu}mt0, the probability of interruption of transfer of the male chromosome per unit chromosomal distance; and {nu}r0, the probability per unit chromosomal distance of a recombinational event. Experimentally these two parameters have the same value (0.06 min-1 or 10-6 per nucleotide pair). Irradiation of the donor parent prior to mating increases the transfer parameter ({nu}mt = {nu}mt0 + {sigma}mtD) and a complete description of the radiation response of recombinant production is obtained by a consideration of the single parameter {sigma}mt. Irradiation of the recipient parent prior to mating increases the recombination parameter ({nu}r = {nu}r0 + {sigma}rD) and a complete description of the radiation response of recombinant production is obtained by the addition of the parameter {sigma}r. Experimentally {sigma}mt and {sigma}r are found to have the same value, approximately 0.004 krad-1 min-1 for X-irradiation. It is thus possible to describe mathematically the behavior of the unperturbed mating system by a single parameter {nu}0; a single additional parameter {sigma} is adequate to describe the behavior of the system when either parental type is irradiated prior to mating. The unexpected observation that {nu}mt and {nu}r have the same value suggests that common molecular mechanisms are involved in the transfer and integration steps.






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Copyright © 1969 by the Biophysical Society.