FIG. 3.

Mutator phenotype of glyU that reads histidine codons. CC105 with plasmid pBR329 (control) and with plasmid pBR329 with the cloned altered glyU was plated on minimal glucose, P-Gal (phenyl β-d-galactoside), X-Gal (5-bromo-4-chloro-3-indolyl β-d-galactoside), and tetracycline plates. Single colonies of the strain with the altered glyU gene contain more blue papillae (28), since they form more Lac⁺ revertants than the strain with pBR329 alone.