Have you ever wondered what kinds of viruses can be found in human waste?
Mya Breitbart and team have been sequencing nucleic acids from fecal samples in order to find out. You might expect that we’d find viruses that infect humans or viruses that infect the bacteria in our gut.
I wouldn’t have expected to learn the result that they found.
A large number, 60% of the viral DNA sequences were from unknown viruses. That’s not a surprise. The surprise came when they looked at the RNA viruses.
Instead, the viral sequences most often came from a plant pathogen called the pepper mild mottle virus or PMMoV, which causes malformation and mottling in pepper plants.
They found PMMoV in three different libraries, all of which were sequenced with high-throughput pyrosequencing by collaborators at the Genome Institute of Singapore: two libraries of RNA viral genes from one individual’s feces at different times and a third library from another individual.
And the pepper virus wasn’t just detected in those two individuals. When the researchers expanded their search to include 18 people from San Diego or Singapore, they found PMMoV sequence in the feces of 78 percent of those living in San Diego and 67 percent of those living in Singapore. It was also detected in every raw sewage sample tested in 11 states.
Are people really eating that many peppers?
When Breitbart and her team tested a variety of foods for PMMoV, they didn’t find the virus in any of the fresh peppers tested. They did find it in several processed foods, though, including chili sauces, chili powder, and Indian curry.
Subsequent experiments indicated that the PMMoV that had passed through the human digestive system could successfully infect plants, suggesting humans unwittingly help the viruses get to their preferred hosts. “We are probably vectors of the virus,” Rosario said.
I guess the viruses like it hot, hot, hot.
Source: Andrea Anderson, “Viral Metagenomics Research Hints at Potential Ecological Influence of Treated Waste,” GenomeWeb News, June 4, 2008.