Understanding Species Interactions of Mixed Consortia for Azo Dye Decolorization: De Wit's Index and Nash Equilibrium

摘要

This study provides a new approach to interspecific competition in constructed mixed-consortia during microbial growth and biodecolorization using De Wit's replacement experiments and game theory. Previous studies (Chen et al., 2003; 2006) proposed that species interactions toward mutualism in mixed cultures were vital to determine optimal decolorization in bioaugmentation. In this study, using De Wit's indices trajectories of relative yields over time, disclosed interspecific competition of the model binary-biosystems in various dye-free and dye-bearing cultures. In aerobic growth, Escherichia coli DH5α owned a growth advantage to out-compete Pseudomonas luteola due to competition exclusion principle. In contrast, in static decolorization DH5a surrendered its advantage to enhance color removal of P. luteola due to the Pareto principle. These two conditions were, in fact, two Nash equilibria (i.e., total conflict and total cooperation situations) according to game theory. In aerobic growth, DH5α had its growth advantage to exclude P. luteola (i.e, conflict strategy). In static-decolorization, to face a common threat of azo dye pollutant, both species inevitably selected cooperation strategy through metabolite stimulation of DH5α to enhance effective decolorization of P. luteola for long-term sustainable management.