Hundreds of new viruses found in river
Researchers have discovered that 97 per cent of viruses in a North Island river catchment were new to science.
No likely human viruseswere detected, but the study suggests that ‘‘only a tiny fraction of the virosphere has been described to date’’.
‘‘The 97 per cent novel figure in itself is not surprising per se, because there has been so little work in this area previously, which means that the viruses we find in these environments are highly likely to be novel,’’ wrote lead author Rebecca French of the Sydney Institute for Infectious Diseases at the University of Sydney.
‘‘However, in general there was a surprisingly high abundance and diversity of viruses found in this study, showing that isolated New Zealand freshwater environments can harbourmany novel and highly divergent viruses.’’
Her team, which included representatives from Massey University, found 504 viruses, of which 491 were probably novel.
If the researcherswere more conservative, they still found 470 novel viruses.
At least 63 of the new species may infect vertebrates (roughly speaking, critters with a backbone and spinal column). In this case, fish and water birds might be infected.
French and her colleagues took water samples from six sites in theManawatū River catchment. Two were from ‘‘pristine’’ sites close to the Ruahine Range.
Twowere taken further downstream, in intensive beef and sheep farming country. The final two were taken near the urban centres of Palmerston
North and Feilding.
The core interest was comparing virus numbers and diversity between sites with different human land uses.
The urban sites had higher diversity (327 virus species) than the farming (150) and pristine sites (119). The urban and farming sites shared some viruses.
The two farming sites had lower virus numbers while the pristine sites had a higher abundance of viruses associated with animals, plants and fungi.
‘‘We identified viruses linked to agriculture and human presence (including possible links to sewage) in the farming and urban sites that were not present in the pristine sites,’’ the academics reported.
The only viruses thatwere previously known were all found in the urban and farming sites, which indicated anthropogenic influence, including agriculture and introduced species.
‘‘Overall, our study shows that human land-use can impact viral communities in rivers, such that further work is needed to reduce the impact of intensive farming and urbanisation on water systems.’’
Another mystery is why the viruses found in the pristine locations didn’t flow downstream.
The researchers used fairly new and powerful techniques, called ‘‘metagenomic nextgeneration sequencing’’, to identify the viruses.
Until recently, viral discovery meant growing a virus in a laboratory, or having some prior knowledge of the virus characteristics or genetic sequence, French said. The new techniques require no prior knowledge of the viruses.
‘‘As viruses likely infect all life forms, and often at high abundance, they can be considered an integral part of global ecosystems,’’ the authors wrote.
Until recently, therewas a strong bias towards studying viruses that infect and somehow damage humans, domestic animals and plants.
‘‘As most viruses do not cause disease in their hosts, characterising non-pathogenic viruses will greatly expand our understanding of the composition of the global virosphere,’’ the authorswrote.
The paper has not yet finished the peer review process and should not be considered conclusive.