Hydrogen formation by an arsenate-reducing Pseudomonas putida, isolated from arsenic-contaminated groundwater in West Bengal, India

Anaerobic growth of a newly isolated Pseudomonas putida strain WB from an arsenic-contaminated soil in West Bengal, India on glucose, l-lactate, and acetate required the presence of arsenate, which was reduced to arsenite. During aerobic growth in the presence of arsenite arsenate was formed. Anaerobic growth of P. putida WB on glucose was made possible presumably by the non-energy-conserving arsenate reductase ArsC with energy derived only from substrate level phosphorylation. Two moles of acetate were generated intermediarily and the reducing equivalents of glycolysis and pyruvate decarboxylation served for arsenate reduction or were released as H-2. Anaerobic growth on acetate and lactate was apparently made possible by arsenate reductase ArrA coupled to respiratory electron chain energy conservation. In the presence of arsenate, both substrates were totally oxidized to CO2 and H-2 with part of the H-2 serving for respiratory arsenate reduction to deliver energy for growth. The growth yield for anaerobic glucose degradation to acetate was Y (Glucose) = 20 g/mol, leading to an energy coefficient of Y (ATP) = 10 g/mol adenosine-5'-triphosphate (ATP), if the Emden-Meyerhof-Parnas pathway with generation of 2 mol ATP/mol glucose was used. During growth on lactate and acetate no substrate chain phosphorylation was possible. The energy gain by reduction of arsenate was Y (Arsenate) = 6.9 g/mol, which would be little less than one ATP/mol of arsenate.