Last Updated on November 3, 2020 by Sagar Aryal
The microbial community of bacteria, viruses, protozoa, and fungi with their collective genetic material present in the human gastrointestinal tract is known as the gut microbiome. The microbiome has a significant role in food and absorption of minerals, fabrication of vitamins, enzymes, amino acids, short-chain fatty acids, guarding against pathogens, and affect human physiology unswervingly or ultimately. This host-gut microbiome interrelation impacts human immune responsive action, metabolism, neuroendocrine activities, and the imbalance in this ratio also leads to disease progression.
The gut microbes were comprised of four major groups of microbes namely they are Firmicute, Bacteroides, Actinobacteria, and Proteobacteria. The commonly colonizing bacteria in the human body are anaerobic in nature. And gut microbiome description provided by cultured methods, metabolic yields of bacteria but these methods are insufficient for determining microbial diversity of microbiome as a big portion of gut microbes remain non-cultivated. The solution is the usage of molecular assays for uncultivable species.
Microbiota metabolic functions
Serotonin is a brain neurotransmitter and also gastrointestinal activity controlling hormone. About 90% of serotonin is synthesized in the gut. This hormone has a vast range of functions but molecular mechanisms of serotonin metabolism are indistinct but its secretion increased by the microbial metabolites by signaling enterochromaffin cells.
Gut microbes gain their energy from dietary carbohydrates which are usually indigestible by the body. And fermentation of oligosaccharides forms short-chain fatty acids which energy source for the host. In adipocytic cells lipoprotein lipase activity inhibited by gut microbes and influenced lipid metabolism.
Xnebiotic drug metabolism
Gut microbes have the potential of metabolizing xenobiotics is discovered 40 years ago and this ability reduces the load of functioning on the liver. Hepatic sulfotransferase activity inhibited by microbial metabolite is an interesting example of microbiome induced drug metabolism is the microbial β-glucuronidase induced deconjugation of the anticancer drug irinotecan that can contribute to its toxicities such as diarrhea, inflammation, and anorexia
Immune system interaction with microbiota
Gut microbiota resides in the gastrointestinal tract delivers health assistance to the host. And changes in their ratio may cause several disorders or autoimmunity in the host. These microbes impact systemic immune response along with the intestinal immune system.
Innate immunity with gut microbes
Antigen-presenting cells co-advance their selves with gut microbiota with features of attacking infectious agents and enduring gut microbes. Experimental results analysis reveals that germ-free animals are neutropenic and also they have less natural killer cells, mast cell, etc which confirms that gut microbes have their immune regulatory role.
Adaptive immune response interaction with microbiota
T helper cell receptors are critical for analyzing the health status of an individual. Th1 cells are significant for intracellular microbial infection removal and Th2 cells have a role in eliminating parasites from the host system. The cell overexpression is fatal and may lead to autoimmunity. This expression of cells regulated by gut microbiota also.
Microbiota composition influenced by human practices
Diet influences highly on the microbial community of gut as observed in the study that individuals taking rich fibrous diet, plant polysaccharides, and low fat have a higher number of Bacteroides species and Prevotella, Xylanibacter bacterial species are extremely important for digesting plant polysaccharides. While firmicutes are high in number in the carbohydrate-rich diet. Short-chain fatty acid molecules having anti-inflammatory properties are raised in a fibrous plant diet.
Microbiota composition alters with hygiene practices, vaccinations, and antibiotic treatments. Antibiotic use reduce Bacteroides and Bifidobacterium while an overgrowth of Campylobacter, Streptococcus, Leuconostoc, or yeast in the microbial community.
Microbial community interfaces are complex among hosts and microbes because their metabolic products influenced the host responsive system. This microbiome engineering could be beneficial for the host system. There are a number of approaches for modifying microbiomes such as the use of prebiotics, probiotics, microbial transplant, drug utilization, etc. The engineered microbiome may release specific molecules such as anti-inflammatory molecules, cytotoxins, protective antigens, etc in the response to suitable stimuli (inflammation, infection, tissue damage, etc.).
Challenges for engineering
Inadequate information for microbial engineering is a limitation for the application of this process. Techniques for identifying microbiome analysis are advanced from simple to metagenomic, transcriptomic, proteomic analysis of microbiome systematically. Gut microbiome engineering safety is questioning and it is influenced by various factors such as diet, social behavior, life span, etc. And these techniques requires data collection from various aspects.