Fig. 6: Proposed ecophysiological advantages and environmental adaptations of F-SOHDs.
From: Versatile nitrate-respiring heterotrophs are previously concealed contributors to sulfur cycle
The red dashed line highlights the toxic inhibition of sulfide on conventional heterotrophic denitrifiers. Purple area indicates the known electron pool generated from OM for heterotrophic denitrifiers, while the blue represents the previously concealed electron pool contributed by toxic sulfide and non-toxic sulfur compounds for F-SOHDs. ∆G0(a) and ∆G0(b) denote standard Gibbs free energy change per nitrate reduction for conventional heterotrophic denitrifiers and chemolithoautotrophic sulfur-oxidizing denitrifiers (equations a and b). ∆G0(c1) and ∆G0(c2) represent standard Gibbs free energy change for F-SOHDs with incomplete and complete sulfur oxidation capacities (equations c1 and c2). These calculations were conducted under the standard conditions (298 K, 1 atm, and 1 M concentrations). The formation energies of each substance were obtained from the standard thermodynamic database provided in CRC Handbook of Chemistry and Physics96. The metabolic rates of cell blooming between F-SOHDs and chemolithoautotrophs are depicted by pink and blue circles.
