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Different Levels of Catabolite Repression Optimize Growth in Stable and Variable Environments

Figure 5

Mutations in global carbon catabolite repression genes give rise to diversified growth behaviors.

Sequencing of the genomes of isolates with shorter lag phases isolated after repeated cycling between glucose and maltose medium revealed mutations in two genes, STD1 and HXK2 (see text for details). (A) Sanger sequencing confirmed the presence of multiple HXK2 mutations and one STD1 mutation in the evolved short-lagged strains. (B) Single-cell lag profiles of independent transformants of the ancestral strain bearing either WT (red and purple traces) or evolved (blue traces) HXK2 alleles. Black traces correspond to the original evolved strains; the finely dotted line is Isolate 1 and the coarsely dotted line is Isolate 2. (C) Same as (B) but for the STD1 allele identified in Isolate 3. Shown in blue are two independent transformants bearing Isolate 3's STD1 allele.

Figure 5