Heterotrophic nitrification by Alcaligenes faecalis: NO2-, NO3-, N2O, and NO production in exponentially growing cultures

Heterotrophic nitrification by Alcaligenes faecalis DSM 30030 was not restricted to media containing organic forms of nitrogen. In both peptone-meat extract and defined media with ammonium and citrate as the sole nitrogen and carbon sources, respectively, NO2-, NO3-, NO, and N2O were produced under aerobic growth conditions. Heterotrophic nitrification was not attributable to old or dying cell populations. Production of NO2-, NO3-, NO, and N2O was detectable shortly after cultures started growth and proceeded exponentially during the logarithmic growth phase. NO2- and NO3- production rates were higher for cultures inoculated in media with pH values below 7 than for those in media at alkaline pH. Neither assimilatory nor dissimilatory nitrate or nitrite reductase activities were detectable in aerobic cultures.