Ammonia and O2 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 NH ₄ ⁺ oxidation, O₂ uptake and NO ₂ ^- production was 1 : 1.5 : 1.0 and for NH₂OH oxidation a ratio of 1 for O₂ : NO ₂ ^- . 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 NH ₄ ⁺ 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 NH ₄ ⁺ 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 NH ₄ ⁺ by cells.Abbreviations mCCCP carbonyl cyanide m-chlorophenylhydrazone - DBP 2,4 dibromophenol - DCCD N-N-dicyclohexylcarbodimide - DIECA Sodium diethyldithiocarbamate - DNP 2,4 dinitrophenol - HOQNO 2-heptyl-4-hydroxyquinoline-N-oxide - NBD chloride 4-chloro-7-nitrobenzo-2-oxa-1,3-diazole - N-serve 2-chloro-6-trichloromethyl-pyridine - PCP pentachlorophenol - 2-TMP 2-trichloromethyl-pyridine - TPB tetraphenylboron - TTFA 1-thenoyl-(2)]-3,3,3-trifluoracetone - KSCN Potassium thiocyanate