Origins of fermentation products formed during growth of Bacteroides ruminicola on glucose.

Bacteriodes ruminicola grown on complex medium with glucose as carbon source gave acetate, CO2, formate and succinate as main fermentation products. No evidence was found for significant glucose catabolism by pathways other than the Embden-Meyerhof sequence. However, [U-14C]glucose fermentation gave products whose specific radioactivities were much lower than expected. There appear to be two main causes. Firstly, a rapid exchange occurred between metabolic intermediates and CO2, probably due to reversibility of the pathway between phosphoenolpyruvate and fumarate. Secondly, non-glucose precursors, mainly peptides and acetate, added to the medium as growth factors, also gave rise to the above end-products. The distortions that such reactions introduce into measurements of ATP molar growth yields based on product analyses and measurements of carbon flux based on radioactivity recovered in products are discussed.