FIG 4.

LdhR decreases exopolysaccharide production. (A) Production of EPS by the WT B. multivorans ATCC 17616 (WT) and the ΔldhR mutant in the presence of different sugars as the main carbon source for 3 days at 37°C. EPS production is expressed as ethanol precipitate (dry weight) (g/liter). A significantly greater amount of EPS was produced by the ΔldhR mutant. *, P < 0.05; **, P < 0.01; ***, P < 0.001 by Tukey's honestly significant difference (HSD) multiple-comparison test. (B) Effect on EPS production by the complementation of the wild-type strain or the ΔldhR mutant by expressing in trans the ldhRA genes from pARG015-1 or the empty vector pBBR1MCS. Cells were incubated in the presence of the indicated sugars for 3 days at 37°C followed by EPS quantification. Significantly smaller amounts of EPS were produced when the ldhRA genes were overexpressed in both WT and mutant strains. *, P < 0.05; **, P < 0.01; ***, P < 0.001 by Tukey's HSD multiple-comparison test.