this study shows that the SBO known as "b. subtilis" can take up residence, live, and reproduce in the bowels. whats interesting is that it talks about the spores. the spores are the bacteria in an infant hibernating state. unlike the full grown bacteria, they are impervious to the stomach acids. but the study's author wanted to see if the spores would simply travel thru the entire intestinal tract and out the other end. what they found is that the spores come to life in the gut and begin to reproduce.


http://jb.asm.org/cgi/content/full/188/7/2692
"Significant levels of germination and sporulation were documented. Using natural isolates of B. subtilis that could form biofilms, we showed that these strains could persist in the mouse gut for significantly longer than the laboratory strain. Moreover, these isolates could grow and sporulate anaerobically and exhibited a novel phenomenon of being able to form spores in almost half the time required for the laboratory isolate. This suggests that spores are not transient passengers of the gastrointestinal tract but have adapted to carry out their entire life cycle within this environment. This is the first report showing an intestinal life cycle of B. subtilis and suggests that other Bacillus species could also be members of the gut microflora."