Extended Data Figure 7. Caffeate utilization by E. lenta and tungstate inhibition of sulfoxide growth enhancement.

(A) GC-MS analysis of supernatant collected from E. lenta DSM2243 grown in caffeate-spiked media. Extracted ion chromatograms of peaks (matched to authentic standards) in uninoculated and inoculated growth media. Proposed reaction pathways are shown, with peaks for each compound provided beneath its chemical structure. The previously characterized hydrocaffeate dehydroxylase may catalyze the observed dehydroxylation reactions. The observed caffeate reduction to hydrocaffeate provides evidence of a caffeate reductase, while the accumulation of m-coumarate suggests that this enzyme may specifically use caffeate. (B) E. lenta DSM2243 growth in media supplemented with formate and different cinnamates. The pattern of cinnamate-dependent growth enhancement supports the conclusions that: (1) dehydroxylation can support respiratory growth and (2) m-coumarate is a poor electron acceptor for E. lenta. (C) The effect of the molybdopterin reductase inhibitor, tungstate, on E. lenta DSM2243 growth. Media was supplemented with formate and the noted electron acceptor, with or without the addition of tungstate. (D) Reactions catalyzed by urocanate and sulfoxide reductases. Tungstate’s selective growth inhibition is consistent with sulfoxide, but not urocanate, reduction being catalyzed by a molybdopterin reductase. Data are mean ±SD (n = 3 independent biological replicates). *p < 0.05, **p < 0.01, *** p < 0.001. Two-way ANOVA, multiple test vs media alone.