FIG. 2.

Mutant accumulation from contaminated seed cultures through three stages of scale-up from 20 to 100 to 500 ml (Scale 1 to 3). The inoculation and sampling methods used are described in Materials and Methods. The lines indicate origins of inocula. Cultures were grown for 48 h in NBY broth (solid triangles), dilute (0.1×) NBY broth (open triangles), and NBY broth containing 0.7 mM CuSO₄ (grey triangles). The values below the symbols are the average percentages (standard errors) of mutants based on 14 replicate broth preparations.