The Human Microbiome in Health and Disease

The human body is a complex assemblage of cells that form tissues, functional organs, and systems. This is the framework upon which complex bacterial communities are built. The body is colonized by a vast number of microbes, collectively referred to as the human microbiota. The analysis of the human microbiota is an exciting and rapidly expanding field of research. In the past decade, the biological relevance of the microbiota for human health has become very apparent. The interest generated has led to an explosion of research in the field but some of the progress has been impeded by some conflicting and inconclusive results. In this chapter, we attempt to convey both the intriguing potential of microbiota research and some challenges currently facing research in the area. We discuss the different techniques available for studying the microbiota, highlighting their advantages and disadvantages. We emphasize the importance of standardizing methods and analyses between centers, to distinguish true variation of the microbiota in unhealthy individuals from normal interpersonal variation. We report on recent literature describing the effect of diet and lifestyle on the microbiota and evaluate the potential role of the microbiota in a range of intestinal disorders. Attempts to manipulate the microbiota are detailed, such as administration of specific bacteria as probiotics, and wide-ranging perturbations of the microbiota by fecal transplantation.