TABLE 4.
Estimation of syntrophic bacterial growth yields based on Gibbs free-energy (ΔGr) calculationsa
| Electron donor | Organisms | ΔGr (kJ/mol donor) | g of cells/mol |
Source or reference | |
|---|---|---|---|---|---|
| YXS,calb | YXS,obsc | ||||
| Lactate | DvH/Methanosarcina barkeri coculture | –61.4 | 3.4 | 6.7 (97)d | 62 |
| DvH/strain 195 coculture | –61.4 | 3.4 | 3.3 (3) | 15 | |
| DvH/strain 195/Methanobacterium congolense triculture | –61.4 | 3.4 | 5.3 (56) | 15 | |
| Butyrate | Syntrophomonas wolfei/Methanospirillum hungatei coculture | –9.1 | 2.3 | 1.36 (41) | 63 |
| Syntrophomonas wolfei/Desulfovibrio G11 coculture | –9.1 | 2.3 | 0.55 (76) | 63 | |
| Syntrophomonas wolfei/Methanospirillum hungatei/Methanosarcina barkeri triculture | –9.1 | 2.3 | 1.08 (53) | 63 | |
| Syntrophomonas wolfei/strain 195 coculture | –9.1 | 2.3 | 2.7 (17) | This study | |
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.
Calculated cell yields (Ycal) were based on the equation Y = 2.08 + 0.0211 × (−ΔG′) (43).
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.
Absolute error E = 3.3 g of cells mol−1; relative error = 0.97; percent error = 97%.