Exposure to a Social Stressor Alters the Structure of the Intestinal Microbiota: Implications for Stressor-Induced Immunomodulation

Exposure to a Social Stressor Alters the Structure of the Intestinal Microbiota: Implications for Stressor-Induced Immunomodulation

The external surfaces of the body are colonized by vast arrays of microbes that outnumber cells of the body by a factor of 10 (i.e., 10¹⁴ bacterial cells to 10¹³ human cells). This means that 90% of the cells of our body are our commensal microbiome. The vast majority of these microbes reside in the intestines as part of the intestinal microbiota, with microbiota levels ranging from < 10⁵ bacteria per gram of digesta in the upper parts of the small intestine, to > 10¹² bacteria per gram of digesta in the large intestine

Many of these bacteria are simple opportunistic colonizers, while the majority are true symbiotic organisms in the sense that they have beneficial interactions with each other and the host. For example, many metabolic activities in the intestines are derived from the microbiota, such as the synthesis of vitamin K and vitamin B complex and the metabolism of carcinogens