Could bacteria-attacking viruses hold a clue to obesity?

Could a barely understood part of the gut microbiome – viruses that attack bacteria, known as phages – shed more light on the microbiome’s role in obesity?

New Zealand researcher Dr Tommi Vatanen, a senior research fellow at the University of Auckland-based Liggins Institute, is exploring this question using a $300,000 Te Pūtea Rangahau a Marsden Fast-Start grant.

Just when we’ve wrapped our minds around the fact that trillions of bacteria living in and on us are right now influencing myriad aspects of our health and wellbeing, another layer of complexity looms into view: the viruses that attack and alter those bacteria, known as phages.

Dr Vatanen says scientific understanding of phages’ role in the gut microbiome is about where understanding of the bacterial microbiome was 10-15 years ago.

“We’ll be learning much more very soon, with many breakthroughs coming.”

Here’s what is known so far: the gut microbiome is involved in functions critical to human health and wellbeing, including metabolism and emotions (in fact, it’s been dubbed our ‘second brain’).The trillions of microorganisms that form it include bacteria, fungi and phages. Phages (from ‘bacteriophage’: literally ‘a thing that devours bacteria’) are generally much tinier and more numerous than bacteria, and there are thousands of different types. 

I expect to find that phage populations in people with obesity will be disrupted, while the healthy donors will have stable and diverse phage populations.

Dr Tommi Vatanen Liggins Institute, University of Auckland

While phages typically kill their bacterial hosts, they can also fuse with the genomes of host bacteria, bringing with them piggyback bacterial genes that can make the infected bacteria more resistant to antibiotics or more virulent. It’s becoming clear that phages can live in a symbiotic relationship with bacteria, where one party benefits while the other is unaffected, in the same way bacteria live symbiotically with their human hosts.

Dr Vatanen will use his award to investigate what happens to phages in fetal microbiome transplantation (FMT), where the poo from a healthy donor is transplanted, either unprocessed or in capsule form, into a person with a health issue. Evidence suggests FMT is a promising therapy for many health disorders, but the way it works remains a mystery.

Liggins Institute
Dr Tommi Vatanen

Dr Vatanen will analyse data from another Liggins Institute study, the Gut Bugs Trial, led by Associate Professor Justin O’Sullivan and Professor Wayne Cutfield. In that pioneering clinical trial, almost entirely funded by philanthropy, young adults affected by obesity took tasteless, odourless capsules containing the filtered poo from healthy donors (screened for harmful bacteria). The trial featured in a TV Three documentary called The Good Sh*t.

“I expect to find that phage populations in people with obesity will be disrupted, while the healthy donors will have stable and diverse phage populations,” says Dr Vatanen.

He hopes to produce initial results by winter 2021.

Director of the Liggins Institute, Professor Frank Bloomfield, says: “This is a fascinating and promising field of discovery with the potential to inform new approaches to a major health issue. The grant reflects the high calibre of research carried out at the Institute, and we congratulate Dr Vatanen on his success.”

The Marsden fund is administered by the Royal Society Te Apārangi and supports innovative research. Fast-Start grants support early career researchers to develop independent research and build careers in New Zealand.

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