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A new pathway for forming acetate during fermentation in bacteria.

B. Zhang




A new pathway for forming acetate during fermentation in bacteria.
B. Zhang*1, C. Bowman1, T. Hackmann1. 1University of California-Davis Davis, CA, 2University of Florida Gainesville, FL.

Acetate is an important VFA formed during fermentation in the rumen. Biochemical pathways for forming it during fermentation in bacteria have been studied for over 80 years. Here, we found a biochemical pathway for forming acetate that was unknown in bacteria. We performed experiments with the skin bacterium Cutibacterium granulosum because its genome does not encode any known pathways. With enzymatic assays, we found it forms acetate and uses a pathway involving 2 enzymes. The first enzyme, succinyl-CoA:acetate CoA-transferase (SCACT), forms acetate from acetyl-CoA. The second enzyme, succinyl-CoA synthetase (SCS), synthesizes ATP. The SCACT/SCS pathway is common in eukaryotes, but it has not been found in bacteria. When we searched genomes for bacteria known to form acetate, we found nearly 1/5 encoded the pathway. The next step is to investigate if this pathway is used by rumen bacteria. The search of genome sequences showed that several rumen bacteria encode the pathway. This includes propionibacteria that are close relatives to the bacterium studied here. The impact of the work is that it can guide genetic engineering or other attempts to manipulate acetate production in the rumen.

Keywords: fermentation, rumen, bacteria.