MUTANTS OF STREPTOMYCES-ROSEOSPORUS THAT EXPRESS ENHANCED RECOMBINATION WITHIN PARTIALLY HOMOLOGOUS GENES

Streptomyces roseosporus mutants that express enhanced recombination b etween partially homologous (homeologous) sequences were isolated by s election for recombination between the bacteriophage phi C31 derivativ e KC570 containing the Streptomyces coelicolor glucose kinase (glk) ge ne and the S. roseosporus chromosome. The frequencies of homeologous r ecombination in the ehr mutants were determined by measuring the chrom osomal insertion frequencies of plasmids containing S. coelicolor glnA or whiG genes. S. roseosporus ehr mutants showed 10(2)- to 10(4)-fold increases in homeologous recombination relative to Ehr(+) strains, bu t no increase in homologous recombination. Southern hybridization anal ysis revealed single unique sites for the insertion of each of the pla smids, and the crossovers occurred in frame and in proper translationa l register, yielding functional chimeric glnA and whiG genes.