Abstract
The human gut plays host to a complex system of micro-organisms. The number of cells in this biomass is greater than the number of human cells in the body. Normal intestinal flora provide a wide variety of benefits to the host organism, including inhibition of pathogenic organisms, nutritional and biochemical effects, and modulation of the immune system both locally and systemically. Although the microflora of an individual are normally highly stable, they can be modified by diet, disease and pharmacological agents. There is growing evidence that these organisms can have significant impact on health and disease, and an understanding of gut ecology may therefore be relevant to clinical practice. This paper reviews the history and literature of intestinal microbiology