ANAEROBIC METABOLISM IN BACILLUS-LICHENIFORMIS NCIB-6346

The products of anaerobic metabolism of glucose and its derivatives sorbitol, gluconate and glucuronate by Bacillus licheniformis have been determined by proton NMR. Glucose was fermented through mixed-acid fermentation pathways to acetate, 2,3-butanediol, ethanol, formate, lactate, succinate and pyruvate. However, the bacterium was incapable of fermenting the three glucose derivatives. When B. licheniformis cells were incubated anaerobically with glucose in the presence of nitrate, the reduced products and formate did not appear and acetate was formed as the major metabolite. Growth and formation of acetate was also observed when B. licheniformis cells were incubated anaerobically with each of the three glucose derivatives, in the presence of nitrate. A formate-nitrate oxido-reductase system was induced under anaerobic conditions, with increased activities when nitrate was added to the anaerobic growth medium. However no activity was detected when cells were grown in the presence of molecular oxygen. Formate-nitrate oxide-reductase activity was absent in chlorate-resistant mutants isolated spontaneously or following Tn917 insertional mutagenesis. The spontaneous mutants fermented glucose in the presence of nitrate suggesting that they were incapable of nitrate respiration, due to a deficiency in one or more components of the formate-nitrate oxido-reductase system. Two insertional mutants exhibited elevated beta-galactosidase activity when grown in the presence of nitrate.