Abstract
There is growing interest in uncovering the viral diversity present in wild animal species. The remote Antarctic region is home to a wealth of uncovered microbial diversity, some of which is associated with its megafauna, including penguin species, the dominant avian biota. Penguins interface with a number of other biota in their roles as marine mesopredators and several species overlap in their ranges and habitats. To characterize the circular single-stranded viruses related to those in the phylum Cressdnaviricota from these environmental sentinel species, cloacal swabs (n = 95) were obtained from King Penguins in South Georgia, and congeneric Adélie Penguins, Chinstrap Penguins, and Gentoo Penguins across the South Shetland Islands and Antarctic Peninsula. Using a combination of high-throughput sequencing, abutting primers-based PCR recovery of circular genomic elements, cloning, and Sanger sequencing, we detected 97 novel sequences comprising 40 ssDNA viral genomes and 57 viral-like circular molecules from 45 individual penguins. We present their detection patterns, with Chinstrap Penguins harboring the highest number of new sequences. The novel Antarctic viruses identified appear to be host-specific, while one circular molecule was shared between sympatric Chinstrap and Gentoo Penguins. We also report viral genotype sharing between three adult-chick pairs, one in each Pygoscelid species. Sequence similarity network approaches coupled with Maximum likelihood phylogenies of the clusters indicate the 40 novel viral genomes do not fall within any known viral families and likely fall within the recently established phylum Cressdnaviricota based on their replication-associated protein sequences. Similarly, 83 capsid protein sequences encoded by the viruses or viral-like circular molecules identified in this study do not cluster with any of those encoded by classified viral groups. Further research is warranted to expand knowledge of the Antarctic virome and would help elucidate the importance of viral-like molecules in vertebrate host evolution.
Highlights
Our knowledge of global viral diversity remains limited, with only a small fraction of viruses known to affect humans and wildlife having been properly described or studied
For the purpose of this study, we focused on the likely eukaryotic viruses that were most closely related to those in the phylum Cressdnaviricota
Using abutting primers designed from the de novo assembled contigs, we amplified, cloned, and Sanger-sequenced 40 viral genomes and 57 viral-like elements
Summary
Our knowledge of global viral diversity remains limited, with only a small fraction of viruses known to affect humans and wildlife having been properly described or studied. Our understanding of diversity in the vertebrate hosts of the Antarctic region remains limited, with early research using serological techniques typically focusing on well-known avian and poultry pathogenic viruses associated with influenza, Newcastle Disease, and infectious bursal disease [3,4,5,6]. Our knowledge of existing Antarctic vertebrate viruses beyond these reports remained constrained until the advent of high-throughput sequencing techniques, uncovering a growing number of viral genomes in the last decade, most recently reviewed by Smeele et al [12] and complemented with the identification of RNA viruses in penguins and their ectoparasites [13]
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