Microbiota: In Health and in Sickness, From Birth to Death

Microorganisms colonize tissues and organs such as the skin and gastrointestinal, respiratory, and genitourinary systems. These microorganisms are generally called as "human microbiota". Human microbiota mostly consists of commensal microorganisms. The commensal microorganisms located on and in the human body are bacteria, fungi, viruses, archaea, and parasites. The microbiota genome is 100 times bigger in size than the human genome. Although the human genome is stationary, microbial genome has a compatible flexible variability during human life. As well as 2-year-old child and newborn, adult and adolescent, the elderly and pregnant woman have a different microbiota. Microbiota and the microbiota genome can be changed by personal and household diet, antibiotic use, mode of delivery, and hygiene within days or even hours, depending on such as these factors. The human immune system and microbiota grow up, develop, and mature as childhood friends by playing with each other from birth to death. Association between microbiota and human is not just related to childhood-it continues with health and disease, until death separates them. This review focused on the roles of microbiota in parasitology, autoimmune diseases, metabolic diseases, and cancer treatment in detail. In addition, inflammatory and immunoregulatory roles of microbiota on the intestinal immune system and how innate and adaptive immune systems regulate microbiota and its content were explained.