TABLE 4

Estimation of syntrophic bacterial growth yields based on Gibbs free-energy (ΔGr) calculationsa

Electron donorOrganismsΔGr (kJ/mol donor)g of cells/molSource or reference
YXS,calbYXS,obsc
LactateDvH/Methanosarcina barkeri coculture–61.43.46.7 (97)d62
DvH/strain 195 coculture–61.43.43.3 (3)15
DvH/strain 195/Methanobacterium congolense triculture–61.43.45.3 (56)15
ButyrateSyntrophomonas wolfei/Methanospirillum hungatei coculture–9.12.31.36 (41)63
Syntrophomonas wolfei/Desulfovibrio G11 coculture–9.12.30.55 (76)63
Syntrophomonas wolfei/Methanospirillum hungatei/Methanosarcina barkeri triculture–9.12.31.08 (53)63
Syntrophomonas wolfei/strain 195 coculture–9.12.32.7 (17)This study
  • a ΔGr (Gibbs free-energy change) was calculated for H2 in the gaseous state at 1.3 Pa (∼10 nM in the aqueous phase). All other compounds were calculated at 10 mM.

  • b Calculated cell yields (Ycal) were based on the equation Y = 2.08 + 0.0211 × (−ΔG′) (43).

  • c Observed cell yields (Yobs) were based on directly measured cell masses (62) or masses converted from protein concentrations by assuming 2 g of cells/g of protein (63) or converted from cell numbers based on the assumption of 6 × 10−13 g per syntrophic cell (15, 43, 63). Percent error values are indicated in parentheses.

  • d Absolute error E = 3.3 g of cells mol−1; relative error = 0.97; percent error = 97%.