The human intestinal microflora (microbiome) is a dense and taxonomically diverse community of microorganisms. While considerable attention has been paid to the bacteria of the intestinal microbiome, relatively little is known about the composition and physiological significance of the bacteriophages that inhabit the human intestine (their collective name, by analogy with the microbiome, is "phageOme"). It is believed that the intestine is home to more than ¹⁰ viruses, which play a crucial role in regulating complex microbial interactions and controlling the numbers of microbial populations.

In February 2019, a paper by Andrey N. Shkoporov and Colin Hill* was published in the journal Cell Host & Microbe, dedicated to methods for studying and characterizing the human phageome. While culture and microscopy were previously considered the primary methods in phage research, today scientists have access to metagenomics and proteomics, which are particularly useful for studying uncultured phages, as well as bioinformatics.

The authors of the article note that the intestinal phageome can vary significantly among individuals, and its composition depends on many factors, ranging from the method of birth (vaginal or cesarean section) to the individual's age. Phages include both lytic and moderate types, and the balance between them is important for maintaining homeostasis in the intestinal mucosa. Changes in phageome composition are observed in various conditions and diseases, including starvation, acquired immunodeficiencies, inflammatory bowel diseases, and others.

Studying the full diversity of intestinal viruses is a complex task, but without them, our understanding of the intestinal ecosystem and its interactions with the host organism remains incomplete.

* Shkoporov AN, Hill C. Bacteriophages of the human gut: the “known unknown” of the microbiome. Cell Host Microbe. 2019; 25(2):195-209. doi: 10.1016/j.chom.2019.01.017 .