Biochemical Functions ofBacillus licheniformisin 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 β -aspartylglycine, breakdown of mucin, conversion of cholesterol to coprostanol and transformation of bilirubin to urobilins. An additional MAC, b-glucuronidase activity, was tested in vitro. β -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 germfree 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 wordis : Bacillus licheniforms , probiotics, microflora-associated characteristics, germ-free mice.