Giant Viruses: Evolution Shows Ancient Viruses Infected Red Algae, Played Key Role in Early Life 1.5 Billion Years Ago [Study]

Giant viruses shocked the scientific community since their discovery in 2003, with their unprecedented size changed our understanding of life and evolution. Until now, the unearthing of these massive pathogens locked in different parts of the world has continued. According to scientists, a virus will only be considered a "giant" if it has a remarkably large genome compared to other viruses.

Viruses, which are considered by some as neither dead nor alive, have remained a challenge for virologists and other scientists in related fields. This means that the exact origin or evolutionary history of viruses remains a mystery, and scientists are still not sure if these microbes are classified as living or non-living. However, a new study shows that giant viruses could have played a significant role in early life.

Ancient Virus Evolution

In the study published in the journal Communications Biology on Tuesday, April 9, researchers from various institutions across the United States, including The State University of New Jersey, analyzed hot spring viruses at Yellowstone National Park. This examination has shed light to ancient virus evolution, which involved prehistoric viruses infecting unicellular red algae, offering clues to early life 1.5 billion years ago.

The research team states that geothermal springs contain red algae that belong to the class Cyanidiophyceae which dominate the microbial community in these sites. To understand the knowledge gap about host-virus interactions in these types of environments, the authors of the April 2024 study studied several habitats such as creek, soil, and endolithic at Lemonade Creek in Yellowstone National Park.

The research paper found that each habitat contains a unique group of viruses, with the giant viruses called "Megaviricetes" being dominant in all three habitats, according to the authors. The findings confirm that hot springs viruses have adapted to thermophilic hosts, organisms that thrive in extremely high temperatures. Furthermore, the results of the study show that red algae at geothermal sites originated 1.5 billion years ago.

The paper states these findings are relevant to understanding biotic interactions of early Earth or the period before the emergence of relatively large living organisms.

Are Viruses Living or Non-Living?

There are varying opinions regarding the nature of viruses, in the context of whether are living or non-living organisms. However, the majority of evolutionary biologists assert that viruses are not alive. One of the main rationales for this argument is that viruses do not meet the characteristics of animate or living things, including growth, reproduction, movement, respiration, excretion, and metabolism.

Furthermore, some scientists say that while a virus uses other cells to replicate itself, it still does not qualify for the said criteria of life. This viewpoint makes most biologists conclude that viruses are never alive at all and are not made out of cells. Regardless of their categorization, viruses are known for causing harmful or life-threatening diseases, such as COVID-19 and avian influenza (bird flu).