Energy conservation by succinate decarboxylation in Veillonella parvula

Veillonella parvula cannot grow with succinate as sole energy source. However, succinate decarboxylation simultaneous with malate or lactate fermentation increased growth yields by 2.4-3.5 g (mol succinate)-1. Malate was fermented stoichiometrically to acetate and propionate whereas lactate fermentation produced more acetate and considerable amounts of H2. Aspartate was utilized only in the presence of succinate as co-substrate. Methylmalonyl-CoA decarboxylase and ATP-dependent pyruvate carboxylase, but not methylmalonyl-CoA:pyruvate transcarboxylase, were detected in cell-free extracts of malate- or lactate-grown cells. The energetic aspects of these fermentation patterns are discussed.