Gargantuan viruses discovered in humans raise questions about life itself

29 Jan 2019

Image: © nobeastsofierce/

Researchers have discovered the largest viruses ever seen in humans, and these ‘megaphages’ are periodically destroying our healthy gut bacteria.

The human gut is a world in itself, a vast ecosystem harbouring billions of bacteria that help us digest our food and maintain a healthy body. However, a new discovery made by researchers from the University of California, Berkeley, has revealed something truly extraordinary.

In a paper published to Nature Microbiology, the researchers proved the existence of viruses – so-called bacteriophages – in the human gut that periodically devastate bacteria during seasonal flu outbreaks.

Unlike standard viruses, these ‘megaphages’ are 10 times larger than the average phage and twice as big as any previously found in humans. Interestingly, these new giants were only found in humans who eat a non-western, high-fibre and low-fat diet. The megaphages were also found in the guts of baboons and a pig, demonstrating to the researchers that they can cross species, potentially bringing disease and antibiotic resistance with them.

“Phage are well known to carry genes that cause disease and genes that code for antibiotic resistance,” said Jill Banfield, who led the research. “The movement of megaphages along with the movement of their host bacteria raises the possibility that disease also can move between animals and humans, and that the capacity for this is much larger with megaphage.”

The megaphage group has been named ‘Lak phage’ after Laksam Upazila in Bangladesh where they were found, but they were also later found in the gut microbiomes of the hunter-gatherer Hadza tribe of Tanzania as well as in baboons in Kenya and pigs in Denmark.

Banfield added that the discovery raises some interesting questions, as, while most biologists consider megaphages not to be ‘living’ – despite being bigger than lifeforms such as bacteria – they blur the distinction between what is alive and what isn’t.

“These huge entities fill the gap between what we think of as non-life and life and, in a sense, we have mostly missed them,” Banfield said.

Colm Gorey was a senior journalist with Silicon Republic