Effects of Carbon Dioxide on Growth and Maltose Fermentation by Bacteroides amylophilus

Abstract

The requirement of carbon dioxide for growth of Bacteroides amylophilus is quantitatively similar to that of certain other rumen bacteria. Carbon dioxide could be replaced by bicarbonate, but not by formate or certain amino acids. Label from ¹⁴CO₂ was incorporated into the succinate produced during maltose fermentation by B. amylophilus, and during glucose fermentation by B. ruminicola, and during cellobiose fermentation by B. succinogenes. All of the incorporated label could be associated with the carboxyl function of the molecule. The depression in radioactivity per micromole of carbon in the succinate formed from the fermentation of uniformly labeled ¹⁴C-maltose by B. amylophilus was greater than would be expected if all of the succinate formed was produced via a direct CO₂ fixation pathway(s) involving phosphoenolpyruvate or pyruvate; the radioactivity per micromole of carbon suggests that as much as 60% of the total succinate results from a pathway(s) involving direct CO₂ fixation. Maltose fermentation by B. amylophilus was dependent upon CO₂ concentration, but CO₂ concentration could not be shown to influence either the fermentation end-product ratios or the proportion of total succinate formed attributable to CO₂ fixation.