RNA Viral Community in Human Feces: Prevalence of Plant Pathogenic Viruses

TLDR

The human gut harbors diverse microbes, including RNA viruses linked to gastroenteritis, yet the enteric RNA viral community in healthy individuals remains uncharacterized. This study aimed to compare the RNA viral composition of fecal samples from healthy humans. Researchers concentrated uncultured viruses by tangential flow filtration, extracted RNA, and constructed shotgun viral cDNA libraries for sequencing. Of 36,769 viral sequences, most matched plant‑pathogenic RNA viruses, with pepper mild mottle virus dominating (up to 10⁹ virions/g), found in 66.7 % of samples worldwide, linked to dietary sources, and shown to be infectious to plants, implying humans may spread plant viruses.

Abstract

The human gut is known to be a reservoir of a wide variety of microbes, including viruses. Many RNA viruses are known to be associated with gastroenteritis; however, the enteric RNA viral community present in healthy humans has not been described. Here, we present a comparative metagenomic analysis of the RNA viruses found in three fecal samples from two healthy human individuals. For this study, uncultured viruses were concentrated by tangential flow filtration, and viral RNA was extracted and cloned into shotgun viral cDNA libraries for sequencing analysis. The vast majority of the 36,769 viral sequences obtained were similar to plant pathogenic RNA viruses. The most abundant fecal virus in this study was pepper mild mottle virus (PMMV), which was found in high concentrations--up to 10(9) virions per gram of dry weight fecal matter. PMMV was also detected in 12 (66.7%) of 18 fecal samples collected from healthy individuals on two continents, indicating that this plant virus is prevalent in the human population. A number of pepper-based foods tested positive for PMMV, suggesting dietary origins for this virus. Intriguingly, the fecal PMMV was infectious to host plants, suggesting that humans might act as a vehicle for the dissemination of certain plant viruses.