. 2015 Jul 28;6(4):e00767-15. doi: 10.1128/mBio.00767-15

TABLE 3 .

Net reactions of metabolisms likely to be important in sputum with sensitivity to pH and metabolic pathway modeling and pH influence^a

Metabolic pathway	Reaction	ΔG°′ (kJ/mol lactate)	ΔE°′ (mV)	ΔG (pH = 4) (kJ/mol lactate)	ΔE (pH = 4) (mV)	Relative effect of low pH	Reaction context in sputum
Aerobic respiration	C₃H₅O₃⁻ + 3O₂ + H⁺ → 3CO₂ + 3H₂O	−1337	1160	−1354	1170	1.3% more energetic	22
Denitrification	5C₃H₅O₃⁻ + 12NO₃⁻ + 17H⁺ → 15CO₂ + 6N₂ + 21H₂O	−1262	1090	−1320	1140	4.6% more energetic	14, 31, 35
Fumarate reduction	6 C₄H₂O₄²⁻ + C₃H₅O₃⁻ + 3H₂O + H⁺ → 6 C₄H₄O₄²⁻ + 3CO₂	−432	370	−449	390	4% more energetic	31
Sulfate reduction	3SO₄⁻² +2 C₃H₅O₃ +8 H⁺ → 3H₂S + 6CO₂ + 7H₂O	−139	120	−207	180	47% more energetic	31
Acetoclastic methanogenesis	C₂H₃O₂⁻ + H⁺ → CH₄ + CO₂	−37^b	48	−54^b	70	31% more energetic	90
Hydrogenotrophic methanogenesis	CO₂ + 4 H₂ → CH₄ + 2 H₂O	−33^b	170	−33^b	170	No effect	90
Acetogenesis	2CO₂ + 4 H₂ → C₂H₃O₂⁻ + H⁺ + 2H₂O	−24^b	123	−19^b	101	20% less energetic	91

^{^a}

Standard reduction potential differences (ΔE^o′) and standard Gibbs free energies (ΔG^o′) were derived from reduction/oxidation half-reactions (51, 89) and calculated at standard temperature (25°C) and pressure (1 atm) at pH 7, indicated by prime notation.

^{^b}

ΔG values for the reactions are per mole H₂ and per mole acetate.