Table 1. Growth parameters and sulfur isotope effects during the growth of DA on sulfide and nitrate in three replicate experiments.

Substrate consumption ratios, yields, and cell-specific consumption rates highlight the differences in nitrate and sulfide consumption. Calculated ³⁴ε values varied depending on whether the substrate (sulfide) or product (sulfate) was used. Uncertainty was propagated from regression uncertainties (see the Supplementary Materials).

Experiment	Growth rate (day−1)		Substrate consumption ratio		Yield estimates [mol C (mol NO3−)−1]				Cell-specific consumption rates (fmol cell−1 day−1)				Sulfur isotope enrichment factor*
	k	σ	HS−:NO3−	σ	Ys	σ	Yc	σ	HS−	σ	NO3−	σ	34ε	σ
1	0.14	0.01	1.42	0.03	0.84	0.06	0.20	0.01	9.8	0.5	6.9	0.3	+13.1	0.7
2	0.25	0.02	1.41	0.05	0.84	0.09	0.39	0.03	9.0	0.8	6.4	0.6
3	0.24	0.03	1.45	0.03	0.90	0.07	0.36	0.02	9.4	1.1	6.4	0.8	+12.0	0.5

*³⁴ε reported in this table is based on Rayleigh enrichment of the substrate pool. See Supplementary Materials and Materials and Methods.