Formate metabolism in the acetogenic bacterium Acetobacterium woodii

Summary Acetogenic bacteria are already established as biocatalysts for production of high‐value compounds from C1 substrates such as H 2  + CO 2 or CO. However, little is known about the physiology, biochemistry and bioenergetics of acetogenesis from formate, an interesting feedstock for biorefineries. Here, we analysed formate metabolism in the model acetogen Acetobacterium woodii . Cells grew optimally on 200 mM formate to an optical density of 0.6. Formate was exclusively converted to acetate (and CO 2 ) with a ratio of 4.4:1. Transcriptome analyses revealed genes/enzymes involved in formate metabolism. Strikingly, A . woodii has two genes potentially encoding a formyl‐THF synthetase, fhs1 and fhs2 . fhs2 forms an operon with a gene encoding a potential formate transporter, fdhC . Deletion of fhs2/fdhC led to a reduced growth rate, formate consumption and optical densities. Acetogenesis from H 2  + CO 2 was accompanied by transient formate production; strikingly, formate reutilization was completely abolished in the Δfhs2/fdhC mutant. Take together, our studies gave the first detailed insights into the formatotrophic lifestyle of A . woodii .