A fantastical world of potential giant viruses lurks beneath the soil

Haircut. Gorgon. Turtle. These all describe shapes of newfound viruslike particles

A collection of three microscopic images of potential giant viruses.

In the loamy soil of Harvard Forest in Massachusetts, scientists have uncovered a new world of potential giant viruses (some pictured in these microscope images), many in unusual shapes.

M.G. Fischer, U. Mersdorf and J.L. Blanchard/bioRxiv.org 2023

Giant viruses may try out all sorts of funky lewks.

New images reveal the varied — and sometimes whimsical — shapes of hundreds of potential soil-dwelling giant viruses. One shape is dubbed “haircut” for its fibers that bristle like freshly buzzed hair. “Gorgon” has tubelike appendages snaking from its shell. And flaps poking out of “turtle” resemble the reptile’s head, limbs and tail, virologist Matthias Fischer and colleagues report June 30 at bioRxiv.org.

These and other peculiar-looking shapes “clearly tell us that we’ve underestimated how structurally diverse these viruses are,” says Fischer, of the Max Planck Institute for Medical Research in Heidelberg, Germany.

Since the discovery of the first giant virus in 2003, scientists collecting genetic material from the environment have uncovered a wide world of giant viruses (SN: 3/21/18). These viruses are roughly 10 to 50 times the diameter of viruses that cause the common cold. The genetic data suggest that giant viruses are diverse, widespread and abundant.

But genetics can’t tell us everything about a virus’s biology, says Steven Wilhelm, a microbiologist at the University of Tennessee in Knoxville. “We don’t know what we’re looking at, who it infects or what it could possibly be doing.”

  1. A microscopic image of a giant virus that resembles a turtle with a purported shell in the middle and five flaps that appear to protrude from it.
  2. A microscopic image of the giant virus particle nicknamed haircut which appears to have fibers attached at the top.
  3. A microscopic image of the giant virus nicknamed "the gorgon" with long tubular-looking structures stick out of a dark central shell.

The new work could help change that, Fischer says. Using transmission electron microscopy, his team analyzed about half a kilogram of soil from Harvard Forest in Petersham, Mass., to produce an image gallery of giant virus diversity — potentially.

Fischer is careful not to call the virus look-alikes “viruses” just yet. The researchers have seen the particles only with a microscope; they haven’t confirmed that the potential viruses can infect particular organisms.

Still, looking at the structures Fischer’s team identified, microbiologist Frederik Schulz of the Joint Genome Institute in Berkeley, Calif., says he’s “convinced that many of these are actual virus particles.”

Scientists can only speculate why giant viruses might form tubular, bristly or turtlelike appendages. They may help the virus infect a host or perhaps move through the environment, Fischer says. “It’s going to be a wild ride … to see what each of these structures do.”

Whatever function they may have, Fischer thinks even more peculiar shapes remain to be discovered. “If a handful of forest soil already contains so many different virus particles,” he says, “this is clearly just the very tip of the viral Mount Everest.”

Meghan Rosen is a staff writer who reports on the life sciences for Science News. She earned a Ph.D. in biochemistry and molecular biology with an emphasis in biotechnology from the University of California, Davis, and later graduated from the science communication program at UC Santa Cruz.

More Stories from Science News on Life