AMMONIA AND O-2 UPTAKE IN RELATION TO PROTON TRANSLOCATION IN CELLS OF NITROSOMONAS-EUROPAEA

The uptake of ammonia and O2 by washed cells of Nitrosomonas has been followed simultaneously and continuously using electrode techniques. The stoichiometry of NH4+oxidation, O2 uptake and NO2-production was 1 : 1.5 : 1.0 and for NH2OH oxidation a ratio of 1 for O2 : NO2-. A variety of inhibitors of electron transport and metals as well as uncouplers restricted ammonia uptake more markedly than O2 utilization. There is good evidence for the involvement of copper in the NH4+uptake process. A quinacrine fluorescence technique has been used to study the proton extrusion by washed cells on adding NH4Cl and NH2OH respectively as substrates. The uptake of NH4+was followed by the extrusion of H+ and this process was depressed by those inhibitors which were also effective in the electrode experiments. A requirement for copper is also established for the translocation of protons into the medium, resulting from the uptake of NH4+by cells. © 1979 Springer-Verlag.