Genetic recombination in Escherichia coli

Abstract

A relation between linkage frequency of an unselected marker and transfer time based on a physical exchange of genetic material was developed for Escherichia coli crosses. Crosses performed under standardised conditions have shown that the relation was valid. The linkage frequency is determined by two constants and one parameter. The constants are the incorporation frequency for donor fragments and the average number of breakage events per unit length. The variable in the relation is the distance in time units between selected and unselected marker.

Citrobacter freundii Mutants Deficient in Host Specificity Functions and Their Recipient Ability for Foreign Deoxyribonucleic Acid

“…However, unlike the non-restricting mutants of S. typhimurium stable integration of chromosomal markers from E. coli Hfr strains has never been observed with the non-restricting C. freundii mutants. Reduced integration or absence of integration of chromosomal markers in matings between heterologous strains has generally been ascribed to differences in nucleotide sequence between donor and acceptor chromosome (Baron, Gemski, Johnson & Wohlhjeter, 1968 ;Verhoef, 1968;Falkow & Formal, 1969). The influence of such differences has been studied extensively by Verhoef (I 968) in matings between E. coli K I 2 Hfr and E. coli c or restrictionless strains of E. coli B.…”

“…It is known that there exist only minor differences between these strains with respect to the location of the genes on the chromosome map and, furthermore, the extent of duplex formation between single-stranded DNA of E. coli B with that of E. coli K 12 is 98% (McCarthy & Bolton, 1963). In homologous crosses of E. coli K 12 Hfr x E. coli K 12 F-the incorporation frequency of a donor fragment is 0.5 (Jacob & Wollman, 1961;De Haan & Gross, 1962;Verhoef, 1968). However, in heterologous crosses between E. coli K 12 Hfr and restrictionless strains of E. coli B F-the incorporation frequency is only 0.019, whereas in E. coli K 12 Hfr x E. coli c F-a value of 0.1 I is found (Verhoef, 1968).…”

“…In homologous crosses of E. coli K 12 Hfr x E. coli K 12 F-the incorporation frequency of a donor fragment is 0.5 (Jacob & Wollman, 1961;De Haan & Gross, 1962;Verhoef, 1968). However, in heterologous crosses between E. coli K 12 Hfr and restrictionless strains of E. coli B F-the incorporation frequency is only 0.019, whereas in E. coli K 12 Hfr x E. coli c F-a value of 0.1 I is found (Verhoef, 1968).…”

General Bacterial Genetics

“…Verhoef & de Haan (51) have reported studies on segregation in a well marked region covering about 20 minutes of chromosomal length. They found that the frequencies of unselected proximal donor markers among re combinants declined exponentially with distance from the selected distal marker.…”

“…Bailey (52) , Wu (53) , Verhoef & de Haan (51) , and Walmsley (54) have derived equations predicting the frequencies of unselected proximal male markers as a function of their distance from the selected distal marker. Bailey (52) and Wu (53) both assume that crossing over is randomly distributed over the chromosomal segment between the selected marker and the Origin and that survival of the selected recombinant class depends on the occur rence of an odd number of crossovers in that segment.…”