Chromosomal Integration of F′ Factors in Recombination-Deficient Hfr Strains of Escherichia coli

Hfr Strains of Escherichia coli K-12

Since the first reports by Cavalli-Sforza (9) and Hayes (24) of strains of Escherichia coli K-12 which are conjugational donors of chromosomal markers at high frequency (Hfr strains), many other Hfr strains have been isolated and our understanding of the mechanisms involved in Hfr formation has increased considerably. All Hfr strains arise from the integration of a conjugative plasmid into the ...

Conjugational recombination in Escherichia coli: genetic analysis of recombinant formation in Hfr x F- crosses.

The formation of recombinants during conjugation between Hfr and F- strains of Escherichia coli was investigated using unselected markers to monitor integration of Hfr DNA into the circular recipient chromosome. In crosses selecting a marker located approximately 500 kb from the Hfr origin, 60-70% of the recombinants appeared to inherit the Hfr DNA in a single segment, with the proximal exchang...

F+ strains of Escherichia coli K-12 defective in Hfr formation.

Dividing and Nondividing Cell Classes of Recombination- Deficient Strains of Escherichia coli

The abilities of rec+, recBrecC-, recA-, and recArecBrecCstrains to support growth of bacteriophage T4, to take up oxygen, and to maintain cell integrity have been measured. (i) With respect to bacteriophage T4 growth, T4 phage is produced with identical lysis time in single-step growth curves with all strains tested. recstrains show reduced phage production (fewer infected centers), but the av...

Thymineless death in recombination deficient mutants of Escherichia coli K12.

When grown in thymine-free minimal synthetic medium, thyA recA mutants of Escherichia coli K12 were comparatively more resistant and thyA recBC mutants more sensitive to thymineless death (TLD) than their respective parent strains. No excessive numbers of single-strand breaks were observed in the DNA of the recBC mutant strain starved for thymine, hence the hypersensitivity for TLD in this stra...