Gnotobiology and the Study of Complex Interactions between the Intestinal Microbiota, Probiotics, and the Host

Gnotobiology technology for the breeding of experimental mice originated in the first half of the twentieth century. Earlier studies conducted in germ-free animals revealed the importance of the microbiota in the development of the immune system, gut morphology, and metabolism. These seminal studies have been confirmed and complemented by recent work that exploits the use of modern gnotobiotic technology as well as the combination of high-throughput molecular techniques to study the composition and metabolic capacity of the intestinal microbiota. From a historical perspective, this chapter discusses the evolution of theory concerning complex host-microbiota interactions and probiotics species. It also reviews the current evidence for a role of maladaptive interactions in the development of disease within and beyond the gastrointestinal tract.