Figure 6.

Lack of BbhI and BbhIV affects cross-feeding behavior of B. bifidum primarily by affecting the ability to release GlcNAc from mucin O-glycans.A, the rate of monosaccharide release into the culture supernatant by the WT, BbhI⁻, BbhIV⁻, BbhV⁻, and BbhI⁻/BbhIV⁻B. bifidum strains. The chemically de-energized cells were incubated in the modified de Man-Rogosa-Sharpe medium supplemented with 0.5% porcine gastric mucin. Monosaccharides were quantified as described under the Experimental procedures section. Symbols and whiskers represent mean ± SD of three independent experiments, with different colors used for respective strains shown above the panel. B, the growth (CFUs) of B. breve in the porcine gastric mucin–supplemented medium. B. breve was incubated without (dashed gray line) or with B. bifidum WT (black line) or BbhI⁻/BbhIV⁻ strain (yellow line). Tetracycline was added to the medium to make B. bifidum cells static. Tet^R was conferred to B. breve by introducing pMSK219. Circles and whiskers represent the mean ± SD of three independent experiments. (C and D) The growth of B. breve on O-glycan-constituent monosaccharides (GlcNAc, Fuc, Gal, NeuAc, and GalNAc: 0.2% each). C, the A₆₀₀ value obtained post 24-h cultivation. The initial A₆₀₀ value was 0.01. D, sugar consumption by B. breve post 24-h cultivation. Sugars were analyzed by high-performance anion exchange chromatography with pulsed amperometric detection. Bar and whiskers represent mean ± SD of three independent experiments. E, O-glycan-constituent monosaccharide concentrations in the culture supernatant of the B. breve monocultivated medium and cocultivated medium with B. bifidum WT or BbhI⁻/BbhIV⁻ strain. Symbols and whiskers represent mean ± SD of three independent experiments. Colors used are as in (B). F, lowered GlcNAc-releasing ability due to the lack of BbhI and BbhIV affects the cross-feeding behavior of B. bifidum.