• Dr Joanne Delange

An Insight into the Gut Virome in Health and Disease


The human gut virome is defined as the total population of viruses, or virus like particles, associated with the gut microbial community, known as the gut microbiota.


The gut microbiota is defined as all microbes associated with human beings, including bacteria, eukaryotes, viruses, fungi, protozoa and archaea. The microbiome denotes the collection of these microbes and their genes. The gut microbiome alone contains more than 1,000 microbial species.


Much research has been conducted investigating the role of the gut microbiota in both health and disease and it has become apparent that microbes play a significant role in health and well-being. Microbes have been shown to provide a range of essential functions, including aiding food digestion and preparing our immune system to provide protection against pathogens. Furthermore, research is showing a connection between dysbiosis and disease.


Human Microbiome Definitions:

To begin to understand investigations of the gut microbiome, sharing precise definitions has become increasingly important.


Microbe – Any microscopic life-form.

Microbiome – The collection of microorganisms (microbes), their genes, and their environmental interactions.

Microbiota – All of the microorganisms (microbes) of a given region or habitat.

Metagenome – Genetic information of the microbiota.

Microbial Communities – Populations of microbes that interact functionally and metabolically.

Dysbiosis – An imbalance in the composition of the microbiota.



Irritable Bowel Syndrome

Irritable bowel syndrome (IBS) is a common disorder that affects the digestive system. It causes symptoms including abdominal pain, stomach cramps, bloating, constipation and diarrhoea. The cause of IBS is unknown and there is currently no cure, however it has been linked to food passing through your digestive system too quickly or too slowly, oversensitive nerves in your digestive system, stress and also a family history of IBS. Because of this dietary changes and medication can help to control the symptoms. Gut bacteria is also known to play an important role in the pathogenesis of IBS.


The Human Gut Virome's Role in IBS

Researchers at the Mayo Clinic, Minnesota, USA have conducted a detailed analysis of the gut virome, including DNA and RNA viruses, which is published in the journal Gastroenterology. In this paper they show how disease, diet and genomics interact with the gut virome in IBS.


Corresponding author, Dr Purna Kashyap explained: 'the virome's role is especially relevant in conditions where the microbiome is considered an essential factor in the development of disease and irritable bowel syndrome is one such condition.'


The gut virome can cause symptoms by direct effects on the gut or by influencing the composition and function of the gut bacteria, which then alter gut function.


The scientists collected data from healthy participants and IBS patients and discovered that the gut virome was relatively stable and unique per individual throughout the six-month study period. They identified IBS-subset–specific changes in bacteriophage populations. Bacteriophages are viruses that are found wherever bacteria exist. Microviridae, Myoviridae, and Podoviridae species were elevated in diarrhoea-predominant IBS, and other Microviridae and Myoviridae species were elevated in constipation-predominant IBS compared to healthy controls.


Dr Kashyap continued: 'This is important as bacteriophages may be responsible in part for shaping the gut bacterial population in these disease subsets and would also be important when considering probiotic therapy… If patients have bacteriophage that can kill the probiotic bacteria – it may not be very effective – do we need to tailor probiotics to match the bacteriophage population?'.


Links were identified between subsets of the virome and bacterial composition and diet. In particular, that the gut virome can be affected by diet and potentially influences interactions with gut bacteria resulting in changes in gene expression. Nutritional Insight wrote an article in September 2019 discussing the positive effects of a vegetarian or vegan diets on the gut microbiota. Research showed that diet is a key factor in influencing human gut microbiota composition, suggesting that a vegetarian or vegan diet is effective in encouraging a diverse ecosystem of beneficial bacteria to support both the human gut microbiome and overall health.


The gut virome was also discovered to be connected with the expression of specific genes linked to immune function in the intestine.


Conclusions

The role of the gut virome is important in conditions when the gut microbiome is an important factor in pathogenesis, such as IBS. Multi-omics analysis has identified a correlation between bacteriophages and gut bacterial composition and function. The bacteriophage population was also shown to be different depending on whether the IBS present was predominately diarrhoea- or constipation-predominant.


This study provides a comprehensive analysis, gathering multi-omics data, including metabolomics, metagenomics, host-transcriptome profiles, and diet measurements to further understand the gut virome in healthy participants and IBS patients.


References:

Mihindukulasuriya KA, et al (2021). Multi-Omics Analyses Show Disease, Diet, and Transcriptome Interactions With the Virome. Volume 161, ISSUE 4, P1194-1207.e8, October 01, 2021. Available at https://doi.org/10.1053/j.gastro.2021.06.077


How disease, diet, and genomics interact with gut virome. Mayo Clinic. Available at

https://newsnetwork.mayoclinic.org/discussion/science-saturday-how-disease-diet-and-genomics-interact-with-gut-virome/

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