A low phosphorylation potential in the acetogen Acetobacterium woodii reflects its lifestyle at the thermodynamic edge of life

摘要

The anaerobic, acetogenic bacterium Acetobacterium woodii grows on hydrogen and carbon dioxide and uses the Wood-Ljungdahl pathway to fix carbon but also to synthesize ATP. The free energy change of acetogenesis from H-2 + CO2 allows for synthesis of only a fraction of an ATP under environmental conditions, and A. woodii is clearly a paradigm for microbial life under extreme energy limitation. However, it was unknown how much energy is required to make ATP under these conditions. In the present study, we determined the phosphorylation potential in cells metabolizing three different acetogenic substrates. It accounts to 37.9 +/- A 1.3 kJ/mol ATP during acetogenesis from fructose, 32.1 +/- A 0.3 kJ/mol ATP during acetogenesis from H-2 + CO2 and 30.2 +/- A 0.9 kJ/mol ATP during acetogenesis from CO, the lowest phosphorylation potential ever described. The physiological consequences in terms of energy conservation under extreme energy limitation are discussed.