Growth ofNitrobacterby dissimilatoric nitrate reduction

Eight strains of the genus Nitrobacter grew under anaerobic conditions in the presence of nitrate. The growth was inhibited by nitrite concentrations above 0.5 mM. By a special culture technique inhibition caused by nitrite was abolished. Nitrite oxidizing cells grew in gas tight culture flasks as a biofilm on a gas-permeable silicone tubing. The biofilm allowed nitrate-reducing cells to grow at a low nitrite concentration. These cells grew either actively motile in the anaerobic medium, or in anaerobic zones of the biofilm. They produced nitrite and ammonia. Nitrogen balance calculations established a loss of inorganic nitrogen for 5 of 8 strains. This implies that nitrate-reducing cells produced furthermore volatile nitrogen compounds. N2O was detected by gas chromatography.