Growth of Nitrobacter by dissimilatoric nitrate reduction

Abstract Eight strains of the genus Nitrobacter grew under anaerobic conditions in the presence of nitrate. The growth was inhibited by nitrate concentrations above 0.5 mM. By a special culture technique inhibition caused by nitrite was abolished. Nitrate 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.