FIG 2 .

Cross-feeding interactions between R. mucilaginosa and P. aeruginosa. M+1, M+2, M+3, M+4, and M+5 indicate compounds that contained 1, 2, 3, 4, and 5 ¹³C atoms, respectively. Error bars, means ± SD (n = 3 bacterial cultures per group). (A) Labeled lactate was found in the R. mucilaginosa (Rm) supernatant but not in P. aeruginosa (Pa) cells. In M9 minimal medium, P. aeruginosa cells contained isotopically enriched pyruvate, alanine, valine, serine, glycine, leucine, and isoleucine. In artificial-sputum medium, P. aeruginosa cells contained isotopically enriched valine, glycine, and isoleucine. (B) Although the R. mucilaginosa supernatant contained only unlabeled glutamate, labeled glutamate was detected in the P. aeruginosa cells grown in artificial-sputum medium and M9 minimal medium. (C to E) Glutamate spectrum for the R. mucilaginosa supernatant (C), P. aeruginosa grown in M9 minimal medium spiked with the R. mucilaginosa supernatant (D), and P. aeruginosa grown in artificial-sputum medium spiked with the R. mucilaginosa supernatant (E).