Biochemical Functions of Bacillus licheniformis in Gnotobiotic Mice

Abstract

A probiotic bacterial strain, Bacillus licheniformis NCTC 13123, has been mono-associated with germ-free mice. After colonization, the following biochemical microflora-associated characteristics (MACs) were analyzed in the large intestinal contents: excretion of short-chain fatty acids (SCFAs), inactivation of tryptic activity, degradation of &#103 -aspartylglycine, breakdown of mucin, conversion of cholesterol to coprostanol and transformation of bilirubin to urobilins. An additional MAC, &#103 -glucuronidase activity, was tested in vitro. &#103 -Glucuronidase activity was not expressed by the bacterium. The amount of total SCFAs was lower than that previously found in germ-free mice. Utilization of individual SCFAs rather than production by the strain may be assumed. The other MACs remained similar to the basal values in germ-free mice. We conclude that B. licheniformis NCTC 13123 is not able to alter any of the microbial functions investigated in vitro or in the gastrointestinal tract of germ-free mice. Whether and to what extent the strain has the capability to interfere with these functions in the presence of other micro-organisms remains to be investigated. Key words : Bacillus licheniformis, probiotics, microflora-associated characteristics, germ-free mice.