Eating Viruses can Power Growth, Reproduction of Microorganism
Published:30 Jan.2023 Source:University of Nebraska-Lincoln
Over a single day, in the placid waters of a single pond, a million virus particles might enter a single-celled organism known for the minuscule hairs, or cilia, that propel it through those waters.
Over the last three years, the University of Nebraska-Lincoln's John DeLong has been busy discovering a potential tide-turning secret: Those virus particles are a source not just of infection, but nutrition.
In a turnabout worthy of Pac-Man, DeLong and his colleagues have found that a species of Halteria -- microscopic ciliates that populate freshwater worldwide -- can eat huge numbers of infectious chloroviruses that share their aquatic habitat. For the first time, the team's lab experiments have also shown that a virus-only diet, which the team calls "virovory," is enough to fuel the physiological growth and even population growth of an organism.
Chloroviruses, a career-defining discovery by Nebraska's James Van Etten, are known to infect microscopic green algae. Eventually, the invading chloroviruses burst their single-celled hosts like balloons, spilling carbon and other life-sustaining elements into the open water. That carbon, which might have gone to predators of the tiny creatures, instead gets vacuumed up by other microorganisms -- a grim recycling program in miniature and, seemingly, in perpetuity.
"That's really just keeping carbon down in this sort of microbial soup layer, keeping grazers from taking energy up the food chain," said DeLong, associate professor of biological sciences at Nebraska.
But if ciliates are having those same viruses for dinner, then virovory could be counterbalancing the carbon recycling that the viruses are known to perpetuate. It's possible, DeLong said, that virovory is aiding and abetting carbon's escape from the dregs of the food chain, granting it an upward mobility that viruses otherwise suppress.
"If you multiply a crude estimate of how many viruses there are, how many ciliates there are and how much water there is, it comes out to this massive amount of energy movement (up the food chain)," said DeLong, who estimated that ciliates in a small pond might eat 10 trillion viruses a day. "If this is happening at the scale that we think it could be, it should completely change our view on global carbon cycling."