The term "Alimentary Microbiome" includes all the micro-organisms constituting the microbial ecosystems in the alimentary tract. Their actions are so closely interrelated with the host body functions that the microbial communities could be considered as like an independent organ of the human body system. Neurological, hormonal and immunological regulation is extended to the microbial populations which in turn secrete molecular messages influencing their host. These microbes also live in closely balanced communities, where the competition is often a secondary goal, if it is striven for at all by the micro-organisms in many alimentary tract surroundings. This book describes the microflora in the mouth and on the teeth, in the gastric areas with low pH, in the upper small intestines where most nutrients are taken up from food, and in the faecal samples as well as in the environment.