Extended Data Fig. 1: Sulfide removal rates at low concentration of sulfide (ca. 50 µM) are higher in ferrihydrite-amended D. alkaliphilus cultures than in abiotic controls.
From: Microbial iron oxide respiration coupled to sulfide oxidation
a, Kinetics of dissolved sulfide during 25-min incubation with ferrihydrite (ca. 62 mM) in the presence or absence of D. alkaliphilus. The incubation experiment was conducted independently with three different cell densities, indicated by optical density at 600 nm (OD600) of the inoculum. Each incubation received three spikes of sulfide at 1.5-h intervals. Two replicates were performed for each condition. OD600 of 0.042 corresponds to an average cell density of 1.38 × 108 cells ml−1. b, Sulfide concentrations in the sulfide-only control of the incubation experiments remained constant. The residual sulfide carried over from the inoculum was subtracted from the measured sulfide concentration. c, The rate constant of sulfide consumption was significantly higher (P < 0.01; two-sided Student’s t-test) in D. alkaliphilus cultures than in abiotic controls. The rate was determined by fitting the first-order rate equation to the measured sulfide concentration changes (see panel a). The center lines and box limits of the boxplot denote the median, and the 25% and 75% percentile of the estimated rate constant, respectively. The whiskers extend 1.5 times the interquartile range from the 25th and 75th percentiles. The two-sided Student’s t-test between biotic (n = 6) and abiotic (n = 6) treatment was conducted for each cell density. P values were adjusted for multiple comparisons (q-values) using the Benjamini and Hochberg method. d, Concentration of HCl-extractable Fe(II) before three consecutive spikes of sulfide to ferrihydrite with or without D. alkaliphilus. The values represent the mean of duplicate culture with OD600 of 0.086. Fe(II) concentration in both treatments increased with repeated spikes of low conditions of sulfide. The treatment with cells produced an excessive amount of Fe(II) compared to the abiotic control. Fe(II) before the 1st sulfide spike results from biological or chemical oxidation of sulfide (ca. 50 µM) carried over from the inoculum.
