GENE TRANSFER BY F′ STRAINS OFESCHERICHIA COLIIV

Abstract

Pittard, James (Yale University, New Haven, Conn.), and T. Ramakrishnan. Gene transfer by F′ strains of Escherichia coli. IV. The effect of a chromosomal deletion on chromosome transfer. J. Bacteriol. 88:367–373. 1964.—Evidence is presented that in an F′ strain of Escherichia coli. AB1206, the chromosomal region corresponding to the merogenote of F₁₄ is deleted. AB1206 differs from all other F′ strains in its stability and in its relative inability to transfer chromosomal markers under conditions in which transfer of the merogenote occurs at a frequency of 100%. Its stability can be accounted for by the fact that the loss of the F merogenote, which contains approximately 10% of the genetic information of the cell, would be a lethal event. The failure of AB1206 to transfer chromosomal markers, except at very low frequencies, can be explained in terms of the crossover model proposed to explain chromosome transfer by F′ strains, since the homologous chromosomal region is missing in this strain. The conclusion that the chromosomal region is deleted is strengthened by the finding that the different enzymes coded for by the genes on F₁₄ are present in AB1206 at the level found in haploid strains, but have double this activity in homozygous diploids carrying F₁₄.