New Giant Virus Jyvaskylavirus Isolated In Finland
For the first time in Finland, researchers at the Nanoscience Center in University of Jyväskylä, Finland, have isolated a giant virus, which was named Jyvaskylavirus. The discovery shows that giant viruses are more common in northern regions than researchers have thought. It also illustrates that there are still many structures whose origins and functions have not been properly studied.
Viruses are everywhere. Most naturally occurring viruses are harmless to humans and can play an important role in the functioning of ecosystems. In recent years, giant viruses have been discovered that can be as large as bacteria. These viruses infect amoebas and other microscopic organisms. Most of the giant viruses identified so far have been found in Europe and South America, and their life cycles and distribution are poorly understood.
The Finnish giant virus has French relatives
The study, initiated at the University of Jyväskylä, is the first to isolate giant viruses from Finland. The giant virus, named Jyvaskylavirus, was discovered when environmental samples were mixed with a culture of amoeba Acanthamoeba castellanii. The virus particle is 200 nanometres in diameter, about twice the size of influenza or coronavirus.
Transmission electron microscopy images of negative stained virus-like particles isolated from Finnish samples. (A) Left, diamond-shaped virions found in a Recirculating Aquaculture System (RAS) tank sample and in experimental aquarium samples. Right, enlarged view showing the virion interior with at least three attachment points to the external capsid. (B) Left, virions with loosely structured capsids found in a RAS tank sample and in experimental aquarium samples. Right, detailed view of one virion of this morphotype. (C) Left, round morphotype found in an experimental aquarium sample; right, enlarged view of a spherical-shaped virion. (D) Left, clusters of full and empty Jyvaskylavirus virions isolated from a composting soil sample. Center, an empty capsid showing the double-layered architecture of Jyvaskylavirus; C marks the capsid and IM marks the putative internal membrane. Right, a fully packaged Jyvaskylavirus virion. — eLife
Through an international collaboration, we elucidated the genome and structure of the Jyvaskylavirus, which was found to be related to Marseilleviruses previously isolated from France. Other new giant viruses were also detected in environmental samples, rejoices professor Lotta-Riina Sundberg from the University of Jyväskylä.
New giant virus regulates microbial populations in soil
The finding indicates that giant viruses are more prevalent than thought in soil and water, even in northern environments.
The discovery will help to understand the interactions between microbes and the role of viruses in regulating populations of all living organisms, as well as providing new insights into the structure of giant viruses, says Sundberg.
IMAGE
Jyvaskylavirus cryo-electron microscopy (cryo-EM) reconstruction. (A) Left, a central slab of the isosurface of the 3D density map, downsampled to a pixel size of 5.36 Å, low-pass filtered to 15 Å, and normalized, showing the interior of the virion color-coded by radius as from key. The white arrowhead marks the membrane bilayer, while the red asterisk highlights the membrane bulging beneath the fivefold vertex. Right, isosurface of half the virion with black arrows indicating the triangulation indices h=7, k=13 (T=309). A threshold level of 0.6 was used in ChimeraX to render both views (Pettersen et al., 2004). (B) Representation of the virion using trisymmetron geometry, with each trisymmetron color-coded differently, and a pentasymmetron marked by a pentagonal black line. (C) A schematic of a virus facet with a trisymmetron marked with a white triangle with three icosahedral asymmetric units (IAU), one of which is marked by a thick black line. The pseudo-hexameric morphology displayed by a capsomer is represented by a hexagon colored in light blue, while the true trimeric state of the major capsid protein (MCP) is depicted as a yellow triangle. To build the IAU (excluding the penton protein), 51 pseudo-hexameric capsomers and one-third of the capsomer located at the threefold symmetry axis are required, resulting in a total of 154 MCPs forming the IAU. The inset shows a cut-through of the density along the threefold axis of a capsomer. (D) AlphaFold3 prediction of the MCP ORF184 shows, with very high confidence, that the fold adopted by the ORF is a vertical double jellyroll. (E) Trimeric model of the capsomers rigid body fitted into the original cryo-EM density and rendered in ChimeraX; left, viewed along the trimer fold axis and on the right, viewed orthogonally to it. The three copies of the MCP are represented in cartoon and colored in green, light magenta, and light blue, while the corresponding density is shown in white transparent surface. — eLife
The study is published in the eLife series.
Genomic and structural insights into Jyvaskylavirus, the first giant virus isolated from Finland, eLife (open access)
Astrobiology, Virology,
