ANAEROBIC METABOLISM IN BACILLUS-LICHENIFORMIS NCIB-6346

The products of anaerobic metabolism of glucose and its derivatives so rbitol, gluconate and glucuronate by Bacillus licheniformis have been determined by proton NMR. Glucose was fermented through mixed-acid fer mentation pathways to acetate, 2,3-butanediol, ethanol, formate, lacta te, succinate and pyruvate. However, the bacterium was incapable of fe rmenting the three glucose derivatives. When B. licheniformis cells we re incubated anaerobically with glucose in the presence of nitrate, th e reduced products and formate did not appear and acetate was formed a s the major metabolite. Growth and formation of acetate was also obser ved when B. licheniformis cells were incubated anaerobically with each of the three glucose derivatives, in the presence of nitrate. A forma te-nitrate oxido-reductase system was induced under anaerobic conditio ns, 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 a ctivity was absent in chlorate-resistant mutants isolated spontaneousl y 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 insertio nal mutants exhibited elevated beta-galactosidase activity when grown in the presence of nitrate.