The thought of the waste-water treatment plant in Klosterneuburg in eastern Austria becoming the center of a news story is rather far-fetched, but that is exactly what has happened, after the discovery of some unusual viruses. However, according to Science Magazine, virologists and evolutionary biologists may one day pay homage to the town’s sewage treatment plant.
The giant viruses found by researchers are four species they have put in a new group dubbed the Klosneuviruses —which they suggest should be classified as a subfamily of the Mimiviridae. The mimivirus genus has only one member, a single identified species named Acanthamoeba polyphaga mimivirus (APMV). However, the genus is a catch-all group because it also refers to a group of phylogenetically related large viruses, designated usually “MimiN”
What’s the big deal about Klosneuviruses?
Science first became aware of giant viruses in 2003, and they really live up to their name. Compared to a typical virus measuring a couple of dozen nanometers in size, giant viruses can reach up to 500 nanometers in size, and maybe more. They can also carry more than 2,500 genes.
Because the genome of giant viruses is so much larger than anything previously seen, some scientists thought they had descended from the fourth domain of life, referencing a view supported by researchers in 2012. There are currently three accepted domains of life, bacteria, archaea, and eukaryotes.
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But size doesn’t necessarily mean the Klosneuviruses should have their own domain, according to some scientists. Evolutionary biologist Eugene Koonin of the National Center for Biotechnology Information in Bethesda, Maryland, is not convinced.
“It’s crystal clear that these giant viruses belong to a group of viruses that includes much smaller ones,” he says. It has been suggested the giant viruses probably evolved from much smaller viruses that picked up bits of a genome from their hosts and like Frankenstein monsters, incorporated the genomes into their own genetic code.
The novel discovery in a sewage treatment plant
Frederik Schulz, a postdoc at the Department of Energy Joint Genome Institute in Walnut Creek, California, along with Austrian scientists were engaged in a project that focused on the diversity of nitrifying bacteria for converting ammonia to nitrate in industrial and sewage waste treatment. During the project, they came across the giant viruses.
Tanja Woyke, DOE JGI Microbial Genomics Program lead and senior author of the paper said, “We expected genome sequences of nitrifying bacteria in the microcolony sequence data. Finding a giant virus genome took the project into a completely new and unexpected, yet very exciting direction.”
Schulz noticed that a number of the giant virus’ metagenomes were viral in origin and after he and Woyke analyzed their source, they discovered the Klosneuvirus group appeared to come from a viral lineage-affiliated with Mimiviruses.
But Koonin is convinced we will discover more giant viruses. “I’m quite confident that the current record of the genome size of giant viruses will be broken,” he says. “We are going to see the real Goliaths of the giant virus world.” That future may come sooner than we think, as scientists continue their search.
This most interesting study was published in the journal Science on April 7 and entitled “Giant viruses with an expanded complement of translation system components.“
