Fig. 4

Optimality degree OptDeg for different growth rates and community compositions of the two-species model (with lactate as substrate for D. vulgaris) for different maintenance coefficients. a 0 mmol_ATP/gDW/h for both organisms, b 4.3 mmol_ATP/gDW/h for D. vulgaris and 0.9 mmol_ATP/gDW/h for M. maripaludis, and c 3 mmol_ATP/gDW/h for both organisms. For case b, the minimum methane production rates (d) and the minimum methane yields referred to lactate (e) are shown