Bistability in a Metabolic Network Underpins the De Novo Evolution of Colony Switching in Pseudomonas fluorescens
Fig 1
The evolutionary history, genotype, and phenotype of 1B4.
(A) The evolutionary lineage from 1A0 (SBW25) to 1B4 consists of nine genotypes (rows). Each consecutive genotype contains an additional mutation (columns: gene and nucleotide change). Grey bars indicate the mutations present in each genotype; grey circles mark the first occurrence. (B) Colonies grown on King’s Medium B (KB) agar for 48 h. 1B4 and 1A0-carB* give dimorphic colonies: opaque (Op) and translucent (Tr; 1B4) or smooth (Sm; 1A0-carB*). Bar ~0.5 cm. Saturation and exposure of images was altered. (C) Light microscope images of cells counterstained with India ink. 1B4 and 1A0-carB* have Cap- and Cap+ cells (white and black arrows). Bar ~4 μm. Saturation and exposure of images was altered. (D) Proportion of Cap+ cells in evolutionary series and engineered genotypes. Introduction of the c2020t carB mutation to ancestors increases capsulation (1A0-carB*, 1A4-carB*). Removal of the mutation from 1B4 (1B4-carBwt) reduces capsulation. Bars are means of five replicates, and error bars denote +/- 1 SE. Two sample t tests for the indicated pairs of genotypes revealed significant differences in capsulation levels (p < 0.001). (E) A 1B4-ΔwcaJ-wzb colony grown on KB medium. Bar ~0.5 cm. (F) A 1B4-wcaJ-lacZ colony grown on medium containing X-gal. Light microscopy was used to check blue sectors contained a greater proportion of Cap+ cells than elsewhere. Bar ~1 cm. Image contrast and exposure was altered.