FIG. 5.

Relationship between zinc concentration and mutant accumulation. NBY broth preparations amended with a range of zinc concentrations were inoculated with a mixture containing 90% wild-type strain CHA0 and 10% spontaneous mutant CHAS17 (A) or CHAS45 (C) or genetically engineered mutant CHA510 (B) or CHA96^rif (D). After 48 h, the percentages of mutants were determined. The values are means based on six cultures; the error bars indicate standard errors. The regression lines approximate 6x² − 26x + 25 (P ≤ 0.0001; r² ≥ 0.93).