Figure Legeneds.
Figure 1. X-gal phenotype and lacI mutations in focal
clones. A representative colony of each clone grown on TGX indicator
plates is shown at left. All mutations across evolved clones were either
a 4 bp insertion or deletion frameshift mutation in a mutational hotspot
region of lacI (box at top). Only the insertion is shown for the
ancestor lacI -, but the deletion was also assessed and had the
same fitness effect and X-gal phenotype.
Figure 2. Fitness effect of lacI- in the ancestor and
evolved genetic backgrounds measured in minimal glucose (purple symbols)
and lactose (green symbols) environments. Asterisks indicate clones
with significantly different lacI - fitness effect when compared
to the effect in the ancestor (Dunnett’s test, P <
0.05). Symbols and error bars indicate mean and standard error of at
least 10 (in the glucose environment) or three (in the lactose
environment) replicate fitness estimates. Note that error bars are
smaller than symbols for many of the glucose fitness estimates. The
dashed lines represent the fitness effect of lacI - in the
ancestor in glucose (dashes) and lactose (dots). Evolution environments
are shown directly above clone names which denotes the population a
clone was selected from (“Anc” indicates the ancestor). In the glucose
environment, one clone had a significantly higher fitness than the
ancestor indicating that compensatory mutations are alleviating the cost
of lacI - in glucose.
Figure 3. Fitness effect of lacI- in ancestor and evolved
clones measured in glucose and lactose environments. Symbols shapes
indicate the evolution environment or genotype of each clone. The
ancestral measurements (circle) indicates the expectation if there were
no epistatic interactions between lacI - and other mutations in
the evolved background.
Figure 4. Plac-GFP reporter expression of lacI+
and lacI- clones in glucose and lactose. The symbols and colors
indicate the genetic background and evolution environment of each clone.
The X-axis shows the genotype and assay environment that Plac- GFP
expression was measured in. Each measurement is the average of the
median expression values of independent replicates (n = 14 in glucose
and n = 4 in lactose). Error bars show standard error of the mean (note
that error bars are generally covered by symbols in the glucose
environment assays).
Figure 5. Relationship between lac expression andlacI- fitness effect. Symbols indicate the mean fitness effect
and lac -reporter expression of the ancestor and evolved clones as
indicated in panel A. A , expression and fitness estimates
measured in the glucose environment. B , expression and fitness
estimates measured in the lactose environment.