“Nature versus Nurture” and the indigenous microbiome

The human microbiome represents the total aggregate of microorganisms within the human body and is recognized as a significant player in human health and disease. The total number of bacteria in humans is nearly 4×10¹³, and although recalculated appraisals of the ratio between human cells and microorganisms has now been reduced and approximates 1:1, the vast quantity of bacteria has an enormous impact in host physiology (1). Healthy development and disease states are closely entwined with the microbiome and examples include obesity, cancer, and also include conditions outside the gastrointestinal tract, such as neurologic and psychiatric illness (2-6). Therefore, understanding the influences on the microbiome is critical to appreciating possible preventative and therapeutic measures for disease.