Giant Viruses With Alien-Looking Appendages, Internal Structures Discovered in Forest Soil

In a small amount of forest soil, scientists made a remarkable discovery of finding a wide variety of giant viruses with unique and unfamiliar shapes. These viruses display alien-like features, including unusual appendages and internal structures previously unseen.

As per Science, the discovery of the giant viruses from a Massachusetts forest soil indicates that this group of relatively large parasites possesses greater ecological diversity and evolutionary significance than previously understood by researchers.

What Are Giant Viruses?

Giant viruses belong to a group called nucleocytoplasmic large DNA viruses (NCLVD) that are distinct from standard virus families in terms of size, structure, genome length, and complexity, according to News Medical Life Sciences.

The original NCLDV family consisted of four viral families: Poxviridae, Asfarviridae, Iridoviridae, and Phycodnaviridae. These families comprise viruses with large double-stranded DNA genomes that replicate entirely within the host cytoplasm and are believed to have a common evolutionary origin, making them a monophyletic group.

As Science reported, giant viruses have sizes comparable to certain bacteria, exceeding 2 micrometers in diameter. Their genomes are exceptionally large, surpassing 2.5 megabases, even larger than those of more complex organisms.

While previous research focused mainly on freshwater giant viruses in algae and amoeba-infecting Mimiviruses, recent DNA sequencing has revealed a vast diversity of giant viruses in other environments, particularly in sediments and soils.

These terrestrial environments are estimated to host about 97% of all viral particles on Earth. The genomic sequencing of soil samples from Harvard Forest has provided evidence of numerous and unique giant viruses thriving in these soils.

Diverse Giant Viruses in Massachusetts Forest Soil

The soil sample was collected from Harvard Forest near Boston and sent to the Max Planck Institute in Germany in 2019 for examination using transmission electron microscopy.

The study, titled "Amazing Structural Diversity of Giant Virus-Like Particles in Forest Soil" available in the preprint server bioRxiv, revealed a rich abundance of giant viruses, up to 635 nanometers in width, smaller than the largest known virus but much larger than typical human-encountered viruses like COVID-19 (50-140 nm).

The researchers expressed high confidence that these structures were viruses due to distinctive capsid shapes, showcasing an astounding diversity of virus-like particles that surpassed all previously isolated giant viruses combined. Below are some of the giant viruses they discovered in the forest soil:

• Exotic giant virus with 'turtle' morphology - large symmetrical limbs;
• 'Medusa' virus with long tubes on all sides;
• 'Gorgon' structure, named after the creature from Greek mythology;
• 'Haircut' category of large viruses with messy heads of fibers.;
• 'Supernova'-shaped viruses with tangled fibers near the capsid shell and arranged tendrils further out;
• 'Christmas star' viruses with double-layered shells resembling interlocking triangles; and
• 'Falcon' viruses with a beak-like structure.

Microbiologist Matthias Fischer, electron microscopist Ulrike Mersdorf, and biologist Jeffrey Blanchard highlight that the discovery of diverse and unique particle structures among soil viruses underscores their intricate nature and genetic diversity. Despite this fascinating insight, much research is needed to unravel the origins and functions of these remarkable entities.

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