FIG 4.

R. palustris NH₄⁺ excretion level affects growth and population trends in cocultures with E. coli NtrC. Shown are growth curves (A to C) and final cell densities normalized to glucose consumption (D) from cocultures pairing WT E. coli (Ec) or the ΔNtrC mutant with R. palustris (Rp) strains with different NH₄⁺ excretion levels. Final cell densities in panel D were taken at the final time points in the respective growth curves in panels A to C, except for cocultures pairing R. palustris ΔAmtB with E. coli ΔNtrC, which were sampled at 260 h. Cell densities were normalized to the levels of glucose consumed to account for incomplete glucose consumption in cocultures containing E. coli ΔNtrC. Cocultures were started with a 1% inoculum of stationary-phase starter cocultures grown from single colonies. Error bars indicate standard deviations (n = 3). Different letters indicate statistical differences (P < 0.05), determined by one-way analysis of variance with Tukey's multiple-comparisons posttest. ND, not determined.