Figure 1
From: A synthetic system links FeFe-hydrogenases to essential E. coli sulfur metabolism
A synthetic pathway linking hydrogenase activity to host viability. A hydrogenase enzyme (HydA) consumes H2 and reduces ferredoxin (FD), a redox carrier protein. Ferredoxin then donates electrons to a plant-type sulfite reductase (SIR), which reduces sulfite to sulfide. With the native sulfite reductase deleted, this pathway becomes the only source of reduced sulfur, an essential metabolic precursor.