The proposed model suggests optimized consumption of carbon sources by G. metallireducens in the environment. At high substrate concentrations, it prefers easily degradable compounds to gain energy for fast growth, while under carbon limitation the spectrum of various de-repressed catabolic enzymes enables quick responses to changes in the substrate composition of habitats. Readiness to express the benzoyl-CoA-degrading pathway suggests that under oligotrophic conditions G. metallireducens co-consumes aromatic compounds and fermentation products.