Table 1 Reaction equations for the three AOA ammonia oxidation pathways

Trans_NH₄

Ammonium transporter

NH₄⁺ → NH₃ + H ⁺_out

Yes

Yes

Yes

AMO

Ammonia monooxygenase

NH₃ + O₂ + QH₂ → NH₂OH + H₂O + Q

Yes

Yes

AMO-NO

Ammonia monooxygenase

NH₃ + O₂ + 2 NO + H₂O → NH₂OH + 2 HNO₂

Yes

HAO

Hydroxylamine oxidoreductase

NH₂OH + H₂O + 4 PCYm → HNO₂ + 4 PCYme + 4 H ⁺_out

Yes

Yes

CuP₄60

CuP460

NH₂OH + 2 H₂O + 5 PCYm + NO → 2 HNO₂ + 5 PCYme + 5 H ⁺_out

Yes

QH₂-Synt

Quinone reductase(QRED)

2 PCYme + Q + 2 H ⁺_out → QH₂ + 2 PCYm

Yes

Yes

Yes

NIR

Nitrite reductase

QH₂ + H ⁺_in  + 2 PCY → Q + 3 H ⁺_out  + 2 PCYe

Yes

Yes

Yes

N₂O-spon

Abiotic reaction

NO + NH₂OH → N₂O + H₂O + H ⁺_out

Yes

Yes

Yes

Cytbc1

Cytochrome bc1; COMPLEX III

QH₂ + H ⁺_in  + 2 PCY → Q + 3 H ⁺_out  + 2 PCYe

Yes

Yes

Yes

Cytaa3

Cytochrome aa3; COMPLEX IV

2 PCYe + 0.5 O₂ + 4 H ⁺_in → 2 H ⁺_out  + H₂O + 2 PCY

Yes

Yes

Yes

ATP-Synt

ATP synthase

4 H ⁺_out  + ADP + Pi → 3 H ⁺_in  + ATP + H₂O

Yes

Yes

Yes

NADH-Synt

NADH reductase; COMPLEX I

QH₂ + NAD + H ⁺_out → NADH + 3 H ⁺_in  + Q

Yes

Yes

Yes