Australia has been isolated from other continents for tens of millions of years and, as such, has developed many diverse biomes. Flora and fauna have adapted to the continent's flat, dry, fire-prone, and nutrient-poor landmass, resulting in a remarkable level of biodiversity that is unique to Australia. While efforts have been made to characterise the overall microbial communities of Australian soils, the Australian soil virome remains largely unexplored. Our study provides an initial snapshot of the diversity, abundance, and composition of RNA viruses in Australian environmental samples. In particular, we asked whether the unique flora and fauna of Australia are mirrored by the presence of unique soil viruses.
Accordingly, we performed meta-transcriptomic sequencing of 16 geographically and ecologically distinct farmland soil and riverbank sediment samples taken from New South Wales and Western Australia, respectively. Despite the relatively small data set, we identified 2,460 putatively novel RNA viruses across 18 orders, 1,780 of which belonged to the microbe-associated phylum Lenarviricota. In several orders, the newly identified viruses were so diverse that they would constitute new viral genera and even families comprised mostly, if not entirely, of novel Australian RNA viruses. Additionally, novel viruses were found between established genera or families, such as in the Cystoviridae and Picornavirales, while highly divergent lineages were identified in Sobelivirales and Ghabrivirales.
Our findings also provide valuable insights into the relationships between soil properties and virome composition, with viral abundance and diversity influenced by sampling site, soil type, and land use. In summary, Australian soils and sediments harbor remarkable viral diversity, reflecting the biodiversity of local fauna and flora. These results lay the groundwork for a nation-wide sampling campaign aimed at characterising the entire Australian soil virome.