The size pH, and redox potential of the cecum in mice associated with various microbial floras.

Cecal size and in situ redox potential and pH of cecal contents were determined in conventionally reared mice and mice reared under a variety of gnotobiotic conditions: germfree, monoassociated with a cecal Clostridium sp., hexaflora-associated and thermoduric polyflora-associated. The mean Eh was approximately +200 mV in germfree and -200 mV in conventional mice. The Eh was close to zero in the monoassociated mice, thus occupying a position intermediate between the germfree and conventional mice. The potentials observed in the hexaflora and the thermoduric flora groups were indistinguishable from those of conventional animals. The degree of normalization was more advanced with respect to the redox potential than to the cecal size in the various gnotobiotic groups. In the thermoduric polyflora-associated group, normalization was observed in both cecal size and redox potential. This demonstrates that normalization can be accomplished with a relatively simplified microflora, at least with regard to the parameters studied.