Figure 1.

Association of the microbiota with humans. Microbiota presents in all parts of our body which has direct contact with external environment. The numbers of bacteria in the mouth (10¹⁰), on the skin (10¹²), and in the distal gut (10¹⁴) are presented in a relation to total number of parenchymal cells (10¹²). The composition of the microbiota in the digestive tract greatly differs in each of specialized compartments as illustrated [6, 13–15]. Physiological functions and chemical environment of each compartment are likely key factors influencing the bacterial habitants.