Abstract
Mutants of Escherichia coli K12 at the capR locus are overproduce capsular polysaccharide, and are derepressed for synthesis of several enzymes involved in capsular polysaccharide synthesis(1-3) including GDP-mannose pyrophosphorylase.(8) UDP-glucose pyrophosphorylase is also derepressed in a haploid capR9 mucoid mutant. Heterozygous mucoid partial diploids with the capR9 allele on the episome and the wild-type (capR(+)) allele on the chromosome (F'capR9/capR(+)) are derepressed for UDP-glucose pyrophosphorylase and GDP-mannose pyrophosphorylase, while the reciprocal nonmucoid heterozygotes (F'capR(+)/capR9) are repressed for these enzymes. These results provide evidence that the episomal capR allele is dominant with respect to synthesis of these two enzymes.
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