SPONTANEOUS AND MUTATOR-INDUCED REVERSIONS OF AN ESCHERICHIA COLI AUXOTROPH I

Open Access
Publisher Website
Google Scholar
Abstract
Spontaneous reversions of an ornithine-requiring mutant of strain W were of four major types: a fast (F) or large colony type, indistinguishable from the wild type; a "slow-48" (S48) type, which requires approximately 48 hr at 37[degree]C to develop large colonies on minimal agar; a "slow-72" (S72) type, which requires approximately 72hr, and a very slow (VS) form, which develops small colonies only after 5-7 days. Growth of the F, S48 and S72 rever-tants in minimal broth was followed photometrically. The S48 and S72 strains exhibited increasing rates of growth during the logarithmic phase. The slow growing revertants responded to ornithine. The S72 revertants mutated to an S48 form with a frequency approximately 1,000 times greater than the frequency of mutation directly from the auxo-trophic state to that of the S48 revertant. A mutator gene increased the frequency of reversion 3,200-fold; all the mutator-induced revertants examined were of the S48 prototrophic type; thus a marked specificity of mutator action was evident.

This publication has 25 references indexed in Scilit: