International Research Journal of Engineering and Technology (IRJET) e-ISSN: 2395-0056 Volume: 07 Issue: 07 | July 2020 www.irjet.net p-ISSN: 2395-0072 © 2020, IRJET | Impact Factor value: 7.529 | ISO 9001:2008 Certified Journal | Page 1280 A Short Review on Various Aspects of Gene Sequencing and Metagenomics to Study Human Gut Microbiome Anirban Goutam Mukherjee 1 , Uddesh Wanjari 2 1 M.Sc Biotechnology (third semester), Vellore Institute of Technology, Vellore, Tamil Nadu, India, 632014 2 M.Sc Biochemistry (third semester), Kamla Nehru Mahavidyalaya, Nagpur, Maharashtra, India, 440024 ---------------------------------------------------------------------***---------------------------------------------------------------------- Abstract - Metagenomics is a word which we commonly hear today. This word has become a part of our day to day lives specifically for a Microbiologist and a Biotechnologist and is not restricted to only these fields but also for various other disciplines. In simple words, metagenomics can be defined as the study of metagenome, actually this means the basic study of the genetic material which is obtained directly from the environmental samples such as soil, water, faeces. This process deals with the genomic analysis of microbial DNA directly from the communities present in the samples obtained directly from microbial communities. Gut microbiota commonly refers to the microorganisms that live in the digestive tract of human beings particularly in the intestine. In humans the gut microbiota comprises of the large number of bacterial species. This number is very large as compared to other body parts. There is often a mutual relationship between the human beings and the gut microflora .This can be established because some human gut organisms benefit the host by fermenting dietary fibers into short chain fatty acids such as acetic acid and butyric acid and these can be easily absorbed by the host. Intestinal bacteria also play an important role in metabolizing sterols, bile acids and xenobiotic compounds. They are also known for producing vitamin B and vitamin K. Therefore it becomes very important to understand the nature of gut microflora as they play a very vital role in a person’s life. Key Words: Metagenome, microbiota, xenobiotics, gut microflora, gene. 1. A COMPLETE REVIEW The microorganisms present in the human gut are known to perform a wide variety of functions. One of the most common is the production of vitamins by the microorganisms [1] . Now these vitamins are absorbed by the host’s large intestine [2,3] .But it is very difficult to understand the complex relationship between the species and vitamin pathway [4,5] . Here the main focus is to understand the contribution of genes that are involved in transport mechanisms and vitamin biosynthetic pathways and how it is related to the corresponding species’ abundance. The main methodology which can be applied is shotgun genome sequencing [1] .This technique was performed with faecal metagenomes of individuals from four different countries. A study of eight B vitamin [6,7] and menaquinone are done .The biosynthetic and transporter genes in healthy subjects from different populations is compared. The whole genome metagenomic sequences are used and a continuous bioinformatic analysis is done. Metagenomic sequences are subjected to the Illumina paired end sequencing and these were obtained from European Nucleotide Archive at EMBL-EBI under the accession number PRJEB2054, PRJNA422434, PRJNA275349, and PRJNA389280 [8,9,10] . Results demonstrate high positive correlations between the species having the genes related to vitamin biosynthetic pathways and transporter mechanisms than that with each of them alone .This clearly indicates that these particular genes are widely distributed among the dominant phyla of the gut species. It is also observed that the total gene abundances remained constant across healthy populations at the global level. But critical analysis from the meta-transcriptomics data explains that the production and utilization potential of these enzymes is very complex and is not merely any direct linear relationship. Therefore it can be said that the species composition and their association with complex metabolic pathway related genes determine the functional genetic content of vitamin metabolism and it’s abundance [11] . It is a proven idea that the gut microbiota is commonly associated with a large number of diseases [12] . The reason for these is widely contributed by many factors. Some of them can include climate, geography, host nutrition, lifestyle and medication [13,14,15] . Therefore it becomes very essential to gain knowledge about the various populations and their habits to get a better understanding and concept of their microbiome .A metagenomic study of intestinal microbiota from the Kazakh donors was conducted. This experiment involved 84 subjects, which includes both male and female, healthy subjects and also includes metabolic syndrome (MetS) patients aged 25–75 years, from the Kazakh administrative centre, Astana [21] . Characterization and description of these microbiomes is done in comparison with a global dataset(832 individuals from five countries on three continents).The correlations between microbiota and various parameters like nutritional data from food frequency questionnaires were explored [16,17,18] . This process involved the extraction of