introduction into escherichia coli wp2 bacteria of a mutation in the gyrb locus previously shown to reduce the degree of chromosomal superhelicity caused a small decrease in the frequency of uv-induced mutations to streptomycin resistance ( but not significantly ) and to tryptophan independence ( mostly ochre suppressors ) in excision repair-proficient bacteria .
C1708726
locus
C0008633
chromosomal