Trillions of microbial cells reside in our intestines, with which we are in permanent interaction. This community, made up of different types of bacteria, eukaryotes and viruses is called the microbiome and participates in various functions such as obtaining energy, absorption of undigested carbohydrates by the human digestive system or the development of immunity, playing a key role in human health and disease.
Therefore, knowing and characterizing the composition of the microbiome is a vitally important tool to understand part of the functioning of our body. Its study and characterization is not simple, since many of the microorganisms in the intestine cannot be cultured outside of it. However, what can be analyzed from fecal samples is their hereditary material. Thus, different metagenomic approaches, based on the analysis of the genome of the organisms resident in the digestive system, study the relationships between the members of the microbiome and their response to certain factors.
For this type of analysis, reference gene catalogs from the human gut microbiome are crucial. Using these libraries, researchers can compare the DNA readings obtained in the samples and identify and quantify the species present. The two main catalogs, MetaHIT and HMP, are based on samples from European and American individuals, but their content is limited.
In the latest issue of Nature Biotechnology , and thanks to the combined efforts of more than 25 research centers, a work has been published on the elaboration of the most complete catalog of reference genes of the human gut microbiome to date. In it, the researchers completed the MetaHIT catalog, adding 250 more European samples, almost 400 Chinese samples and more than a hundred American samples. The catalog includes almost 10 million non-redundant genes and is very close to reaching saturation, that is, to include all the information on the function of the genes of the microbiome.
The analyzes show differences in the microbiota of the different populations in aspects such as nutrient metabolism and xenobiotic detoxification, which may have been modeled with the diet and environment of these populations. However, the different genetic architecture of the populations is not completely ruled out.
The information contained in the catalog can be viewed on the website http://meta.genomics.cn . And for microbial diversity not included in this catalog, as well as the identification of new microorganisms, in the same issue of Nature Biotechnology , a team from the Technical University of Denmark describes a method to identify and assemble genetic material without resorting to genomes reference.
Like the genome contained in human cells, information obtained from the microbiome brings researchers closer to understanding variability between populations and its influence on health and disease.
References:
Li J et al. An integrated catalog of reference genes in the human gut microbiome . Nat Biotechnol. 2014 Jul 6. doi: 10.1038 / nbt.2942.
Nielsen HB et al. Identification and assembly of genomes and genetic elements in complex metagenomic samples without using reference genomes . Nat Biotechnol. 2014 Jul 6. doi: 10.1038 / nbt.2939.
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