Scientists have compiled* the most comprehensive catalog to date of bacteriophages inhabiting the human intestine. They have identified over 142,000 bacterial virus genomes and identified some of their characteristics.

Bacterial viruses—bacteriophages—are the most numerous biological entities on Earth. They are present wherever bacteria are found, including the human intestine. Bacteriophages play a vital role in the functioning of microbial communities, specifically by regulating bacterial numbers and mediating horizontal gene transfer between bacteria. Given the vital role of the intestinal microbiota in the functioning of the human body, it is not surprising that not only intestinal bacteria but also their parasites—bacteriophages—are of growing interest to scientists.

New high-throughput sequencing technologies (DNA sequencing) have enabled scientists to identify numerous new viruses in the human gut, including those difficult to classify according to the taxonomy established by the International Committee on Taxonomy of Viruses (ICTV). Scientists from the Sanger Institute and the European Bioinformatics Institute (EMBL-EBI) (UK) used metagenomics methods to analyze 28,060 gut microbiota samples collected in 28 countries across Europe, Asia, the Americas, Africa, and Oceania, as well as 2,898 bacterial genomes from the human gut. The samples yielded 142,809 genomes of phages inhabiting the human gut, more than half of which had not previously been described.

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The greatest diversity of bacteriophages was found in bacteria of the Firmicutes phylum, which includes lactobacilli, clostridia, staphylococci, and streptococci. In the samples, the scientists identified representatives of a new, diverse phage clade, which they named Gubaphage. Gubaphage infects Gram-negative, anaerobic, rod-shaped bacteria of the Bacteroidaceae family.

Scientists discovered that the phageomes (the collection of phage genomes in a sample isolated from a single organism, named by analogy with the genome, microbiome, and proteome) of residents of North America, Europe, and Asia differ from those of residents of Africa and South America. Moreover, the phageome composition correlated with certain lifestyle differences, such as differences in the phageomes of urban and rural residents.

The study's authors note that they have taken an important step toward understanding the human microbiome and the role of viruses in its evolution and functioning.

* Camarillo-Guerrero LF, Almeida A, Rangel-Pineros G et al. Massive expansion of human gut bacteriophage diversity // Cell, 2021; 184 (4): 1098. DOI: 10.1016/j.cell.2021.01.029