Fig. 1

The denitrification phenotype across the RSSC. a Growth and production of nitrogen gas under anaerobic condition. Values represent the ratio of O.D.₆₀₀ readings following 72 h of anaerobic incubation in VDM plus 30 mM NO₃ ⁻ vs. without added NO₃ ⁻. A value above 1 indicates that in the presence of NO₃ ⁻ a strain reached higher optical densities than in the absence of NO₃ ⁻, indicating NO₃ ⁻ respiration enhanced growth. A value above the arbitrary threshold of 2 meets our cut-off for biological significance. Strain names in green and green ‘+’ s indicate N₂ gas was produced within 96 h of anaerobic inoculation in VDM + 30 mM NO₃ ⁻. Production of N₂ indicates that the strain completed the full denitrification pathway as indicated by production of visible N₂ gas bubbles. Bars indicate standard error. Data represent the means of 4–6 biological replicates. b Summary of the presence/absence of denitrification genes. Black/gray cells indicate the presence of a gene in all the sequenced strains of this group and white cells indicate its absence