Influence of high luminal P_O2 on the anaerobic bacteria of the rat colon

The influence of high luminal P_O2 on Colonic anaerobes was investigated by chronically perfusing the colon of unrestrained rats with O₂ or N₂. A luminal P_O2, of approximately 700 mm Hg did not significantly influence the fecal concentration of total anaerobes recovered on rabbit blood agar or of Bifidobacterium sp. and Bacteroides sp. recovered on selective media. However, the O₂ infusion reduced the rat's excretion of CH₄ (a metabolic product of anaerobic bacteria) to about 5% of the control value, although the feces of O₂-treated rats produced CH₄ normally. This study suggests that the production of metabolites by the Colonic bacteria may sometimes be more accurately studied in situ rather than in culture. Measurement of volatile bacterial metabolites in breath may provide a simple means of studying the in situ metabolism of a variety of colonic bacteria in man.