Megaphages discovered via microbiome sequencing

For the first time, scientists have discovered a class of phage with over 540 kilobases per strain, as isolated from human microbiomes in Bangladesh and Tanzania, as well as African baboon and Danish pig microbiomes. These newly discovered phages (termed Megaphages) have genomes almost 10 times larger than their phage compatriots and are approximately 200 to 300 nm across. This scale makes megaphages on the same size scale as Mycoplasma bacteria and Poxviridiae viruses. 

This megaphage was isolated from a resident microbiome bacterium of Prevotella, which is capable of being pathogenic to humans. However, within the microbiome, Prevotella are found to be localized in the gut of individuals who eat common non-Western diets (including high-fiber, low-fat foods).This connection was made after it was observed that the Lak Megaphage family and Prevotella had a predator-prey population cycling relationship, where it appeared that Lak proliferation induced Prevotella cell death, and Lak phage population plateaued as Prevotella populations began growing again. Over time, this observation was shown to be consistent with the non-Western diet and their research in baboons suggest that these megaphages are becoming more and more prevalent in primate communities, especially those that prescribe to the high-fiber, low-fat diets.

Beyond the fascinating discovery detailed in the Nature Microbiology article, the discovery of megaphages may have significant impact on human disease. The authors of this paper state that 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.” Given the impressively large genome of these megaphage, it is thought that they may have much wider capacities for mutation and differentiation, such that they could infect and cause disease in a wide variety of hosts, like humans. It was noted that many of the genes present in the large genome would potentially allow these phage to subvert bacterial defense mechanisms, suggesting these viruses may be highly adaptable to become pathogenic given their genomic flexibility. Further, the widespread nature of these megaphages suggest that presence in primates (as was the case for baboons and the microbiomes of humans) may propose Lak phages as a target of significant research for prevention of future disease.

~Kyle Enriquez

Sources:

https://news.berkeley.edu/2019/01/28/whopping-big-viruses-prey-on-human-gut-bacteria/

https://www.nature.com/articles/s41564-018-0338-9