Abstract
The relations between volatile components and bacterial flora in mouse caecum were studied in germ-free, gnotobiotic and SPF mice and in gnotobiotes given heated caecal homogenate from SPF mice. Anaerobic fusiform bacteria were present in SPF mice and ex-gnotobiotic (gnotobiotic plus SPF caecum) mice only. Low concentrations of furfural correlated with the presence of intestinal fusiform bacteria, suggesting that furfural may be decomposed by these organisms. Fusiform bacteria were also associated with the highest concentrations of acetic and butyric acids and may play an important role in regulating the composition of the mouse caecal flora.