Interaction of the microbiota with the human body in health and diseases

Abstract

The human body contains many microorganisms, including a large number of bacteria, viruses, fungi, and protozoa, which are referred to as the microbiota. Compared with the number of cells comprising the human body, that of the microbiota has been found to be much larger. The microbiome is defined as microorganisms and their genomes have been shown to contain about 100 times more genes than the human genome. The microbiota affects many vital functions in the human body. It contributes to regulation of the immune system, digestion of food, production of vitamins such as B12 and K, metabolization of xenobiotic materials, and many other tasks. Many factors affect the microbiota biodiversity, such as diet, medicines including antibiotics, relationships with the environment, pregnancy, and age. Studies have shown that the lack of microbiota diversity leads to many diseases like autoimmune diseases such as diabetes type I, rheumatism, muscular dystrophy, problems in blood coagulation due to lack of vitamin K, and disturbances in the transfer of nerve cells due to lack of vitamin B12, in addition to its involvement in a number of conditions such as cancer, memory disorders, depression, stress, autism, and Alzheimer's disease. The aim of this review is to summarize the latest studies discussing the relationship between the microbiota and the human body in health and diseases.

Keywords: dysbiosis; gut microbiota; immune system; infectious diseases; metabolic disorder; probiotic.

Fig. 1.

Factors influencing the pediatric microbiota up to 3 years of age.

Fig. 2.

Immune system mechanisms that maintain intestinal homeostasis.

Fig. 3.

Interaction between xenobiotic materials and the gut microbiota.

Fig. 4.

Gut dysbiosis allows C. difficile (CD) to grow and secrete toxins that destroy epithelial cells.

Fig. 5.

H. pylori virulence factors induce disease. Urease secretion reduces gastric acidity, and flagella and toxins help penetrate stomach epithelial cells and cause infection.

Fig. 6.

Relationship between the intestinal microbiota and metabolic disorders.

Fig. 7.

Effects of microbiota dysbiosis and alcohol consumption on the liver.