Studies on the mechanism of chromosomal transfer and genetic recombination in Escherichia Coli K-12

• Main Author: Gross, Julian David
• Published: Imperial College London 1963
• Subjects: 579.3
• Online Access: https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.602205

In a general introduction present-day knowledge of conjugation and genetic recombination in Escherichia coli K-12 is surveyed, and the relevance of the results of the experimental investigations presented later is indicated. The studies leading to an understanding of the determination of mating types, and the available information concerning the formation of union between mating cells and the ensuing transfer of genetic material are described. The final section summarises the various approaches used to analyse the mechanism of genetic recombination after conjugation, and the results that have been obtained. The experimental section contains the results of investigations into several aspects of the conjugation process. The first part describes a new and convenient method for studying the kinetics of genetic recombination and its application to the problem of the mechanism of recombination. In the second and third parts, various questions relating to multiple matings i.e. matings between groups of cells of greater complexity than individual pairs, are examined; it is shown that two donor cells can transfer genetic material simultaneously to the same recipient cell and that recombinants deriving genetic information from all three parents can be formed, probably by a recombination process involving simultaneous genetic exchange between all three genetic structures; it is also shown that simultaneous mating between a recipient cell and several donor cells can lead in certain oases to death of the recipient tell, perhaps as a result of cumulative damage to the cell surface. The final 'section,'which is in the form of a published paper, describe work carried out in collaboration, with Dr. P.G. de Haan on the kinetics of chromosome transfer during conjugation. This work demonstrates the existence of a variable delay between the time when donor and recipient cells come into contact and the time when transfer of the donor chromosome is initiated. In addition, evidence is presented that the segment of chromosome which has penetrated from donor to recipient cell may be withdrawn when the mating cells separate.