Since the development of Holobiont worldview, it has become difficult to see species living in isolation: there are many points of interaction that favor collaborative survival strategies among organisms. One such example may be observed in so-called killer yeasts, where cells are provided with biocidal properties by a system of double-stranded RNA (dsRNA) viruses. The goal of this research was to find such symbiotic groups throughout wild Saccharomycetales yeast and define their virome by homologically overlaying the indicated viral sequences, and analyzing them using bioinformatic tools. The unveiled findings may assist us in comprehending interspecies communication and viral transmission within distant biological organisms.
Our group evaluated 407 wild yeast strains from various natural environments in Lithuania. Incubation on selective medium and RNA gel electrophoresis revealed that more than 10% (N = 47) of the selected colonies exhibited a killer phenotype. Only yeast belonging to different species were investigated further. Twenty distinct dsRNAs were obtained after purifying viral genomes from the chosen strains. They were all sequenced using Oxford Nanopore Technologies and characterized by applying CLANS (CLuster ANalysis of Sequences) tool. The findings show that a broader range of viruses — not only belonging to yeasts — are present in different strains, including non-yeast totiviruses and Mitoviridae sp., generally found in filamentous fungi. This implies that dsRNA genomes are considerably more distributed throughout the organisms and that their modes of function are yet to be deciphered.