Fig. 5: Arginine and ArgR regulate mucoidy by increasing rmpD transcription and decreasing capsular polysaccharide chain length diversity.

KPPR1 and the ∆argR mutant were cultured in different amino acid conditions (M9 + All, M9-Arg, M9 + Glyc, M9 + Glyc + Arg) or (M9 + All), respectively. A, C, E Capsular polysaccharides (CPS) were separated on a 4-15% SDS-PAGE gel and stained with Alcian blue and silver stain. Three distinct polysaccharide types emerged: diverse mid- to high-molecular-weight chains (Type A), uniform high-molecular-weight chains (Type B), and diffuse ultra-high-molecular-weight chains (Type C). Data presented are the mean, and error bars represent the standard error of the mean. Representative images of the three independent gels are shown in panels (A, C and E) with the quantification of three independent replicates being shown in panels (B, D, and F) ImageJ was used to quantify each CPS chain type with background subtracted. To minimize gel-to-gel variability, the control and experimental density values were extracted from the same gel and used to calculate fold-change abundance. Changes in CPS type production were determined by calculating the fold-change in experimental density values relative to control density values on three independent gels. Statistical significance was determined using a two-tailed one sample t-test. p-values are displayed above each comparison; * p < 0.05; *** p < 0.001. Exact P-values: (B) left to right: 0.0474; (D) left to right: 0.0010, 0.0289; (F) left to right: 0.0488, 0.0161, 0.0107. Experiments were performed ≥ 3 independent times (n = 3). Source data are provided as a Source Data file.