TABLE 1.

Definition of the rate laws governing the reactions shown in Fig. 4

Expression	Description	Explanation of terms
$k_{H2S}=v_{\max }\frac{\left[{\text{H}}_2\text{S}\right]}{K_m+\left[{\text{H}}_2\text{S}\right]}$	Rate of H2S oxidation by SQR	Km (38 ± 1.2 μM) and νmax (biomass dependent) were derived by fitting the data below AnoxyPmax in Fig. 2 and 3 and Fig. S8 in the supplemental material.
$k_{anoxy}=k_{H2S}\frac{{\text{PQ}}_{\text{ox}}}{K_{SQR}+{\text{PQ}}_{\text{ox}}}$	Rate of PQ reduction by SQR	PQox refers to the oxidized part of the total PQ pool. KSQR describes the apparent affinity of SQR for oxidized PQ.
$k_{oxy}=I_{\text{PSII}}\frac{{\text{PQ}}_{\text{ox}}}{K_{PSII}+{\text{PQ}}_{\text{ox}}}$	Rate of PQ reduction by PSII	KPSII describes the apparent affinity of PSII for oxidized PQ. IPSII determines the rate of exciton generation by the light energy harvested in PSII, for which we assume a linear relationship to electron transport at a given redox state of the PQ pool for the nonsaturating light intensities used in our experiments. IPSII also defines the maximum rate of oxygenic P, i.e., OxyPmax.
$k_{PSI}=I_{\text{PSI}}\frac{{\text{PQ}}_{\text{red}}}{K_{PSI}+{\text{PQ}}_{\text{red}}}$	Total rate of photosynthetic electron transport	KPSI describes the apparent affinity of PSI for reduced PQ. IPSI describes the rate of exciton generation by the light energy harvested in PSI and determines the maximum rate of kPSI, i.e., AnoxyPmax. The model assumes that at steady state, kPSI is equal to koxy + kanoxy.