During growth in the retentostats with acetate plus benzoate, the benzoyl-CoA pathway was the only aromatic compounddegrading pathway expressed. In contrast to high growth rates, benzoyl-CoA ligase (Gmet 2143) was not detected in retentostats, while succinyl:benzoate coenzyme A transferase (Gmet 2054) was highly abundant (Supplementary Table S1). Proteins degrading toluene were only detected at high growth rates (Supplementary Table S1 and Fig. 4).