Anaerobic Culturing of Clostridia Strains

The strains used in this study are listed in Table S3. Strains were cultured on brain heart infusion (BHI) agar or broth (Oxoid) at 37°C in an anaerobic chamber (Biomerieux, Marcy l’Etoile, France) (v/v: 80% N₂, 10% H₂, 10% CO₂). When necessary, the medium was supplemented with cycloserine (250 mg.mL⁻¹), thiamphenicol (15 mg.mL⁻¹ to select KO strains or 7.5 mg.mL⁻¹ to maintain the plasmid pMTL007-hbd), or erythromycin (5 mg.mL⁻¹). Escherichia coli TOP10 strain was used for cloning and plasmid propagation. E. coli HB101 (RP4) strain was used as the conjugative donor for developing the clostridia KO strains. E. coli strains were cultured aerobically at 37°C in Luria–Bertani agar or broth, and when needed, the medium was supplemented with ampicillin (100 mg.mL⁻¹) or chloramphenicol (25 mg.mL⁻¹).