FIG. 3.

Effect of various ratios of analogue to natural tryptophan on the growth of parental and evolved clones. Clone B7-3 (◊) and parental C600p (□) were grown on various ratios of 4fW (left), 5fW (center), and 6fW (right). Growth rates for clones were determined by fitting the log portion of growth curves to the following equation: y = a log x + b, where a was the growth rate (see Materials and Methods). The evolved clone B7-3 had a growth advantage for all ratios of 4fW to W, including a ∼10-fold increase on 99.97% 4fW.