Fig 1.

Effect of iron and ammonium limitation on growth (left) and sulfide production (right) of DMSS-1 grown on lactate (upper) and malate (lower). Each line indicates a single independent experiment. Both control and nutrient-limited cultures produced similar amounts of sulfide at the end of the incubation, indicating that iron and nitrogen limitation caused a reduction of overall growth rate and not an extended lag phase followed by the same growth rate. For malate-grown iron-limited cultures, the incubation was stopped before the cessation of growth (see Materials and Methods). Concentrations of iron and ammonium were estimated at the beginning of the incubation. Cell density is subject to a ±15% error, and the analytical uncertainty of the measurement of sulfide concentrations is ±5%.