Selection of mutants of Escherichia coli constitutive for tryptophanase.

Proc. Natl. Acad. Sci. U.S. 40:1064, 1954). The galactose mutations are of the same stability as the streptomycin-sensitivity gene. Some 60 other galactose mutants are similar to those reported in Table 1. No instances of mutability grossly higher than Gal16 or Galg have been noted, and no certain cases of failure to revert have been found. Combinations of Gal mutations have been synthesized via lambda-phage transduction. Such combinations have never been observed to revert, and the combined independent probabilities (ca. 10-2) indicate why this is so.