Fig. 2.

Model output from simulations with (black dashed lines) and without (red solid lines) cryptic sulfur cycling active. The half-saturation constant for nitrate in the dissimilatory nitrate reduction to nitrite pathway is increased to 80 μM to induce sulfate reduction and, consequently, initiate cryptic sulfur cycling. Chemical profiles are as labeled, and sox, nap, narG, nirK, and dsr genes correspond to aerobic sulfide oxidation, sulfide oxidation by nitrate, organotrophic dissimilatory nitrate reduction, organotrophic dissimilatory nitrite reduction, and dissimilatory sulfate reduction, respectively.