Formation of heterozygous tandem duplications in conjugational recombination in Escherichia coli: study of the effect of mutations for the recQ, urvD, and recJ genes

摘要

Stable tandem duplications were shown to originate from conjugational recombination between Esteen Escherichia coli HfrH strains carrying mutations for the deo operon. The duplications deoC deoD/deoA deoB:: Tn5 usually constitute approximately 5percent of the Deo~+ offspring. The effect of mutations for the recQ, uvrD and recJ genes on the frequency of duplications was studied. The CM1563 strain carrying the recQ mutation was shown to give, as a recipient, 20percent of duplications in the Deo+offspring. However, this property of CM1563 seems to depend on the presence of a spontaneous mutation of unknown nature, which also increased UV sensityvity of bacteria. The recQ mutation itself increased the frequency of duplications by less than 50percent. The recJ mutation did not virtually affect the frequency of duplications. The uvrD mutation possessing the recombinogenic effect was shown to increase the frequency of deo~+recombinants and simultaneously decrease the frequency of duplications. Tandem duplications are assumed to be normal intermmediates of multi-stage conjugational recombination initiated by the integration of the proximal region of the Hfr chromosome into different nongomologous regions of the recipient chromosome.