Single-Stranded DNA Viruses in Antarctic Cryoconite Holes.

Pacifica Sommers,Steven K Schmidt,Rafaela S Fontenele,Simona Kraberger,Dorota L Porazinska,John L Darcy,Arvind Varsani,Tayele Kringen

doi:10.3390/v11111022

Abstract

Antarctic cryoconite holes, or small melt-holes in the surfaces of glaciers, create habitable oases for isolated microbial communities with tightly linked microbial population structures. Viruses may influence the dynamics of polar microbial communities, but the viromes of the Antarctic cryoconite holes have yet to be characterized. We characterize single-stranded DNA (ssDNA) viruses from three cryoconite holes in the Taylor Valley, Antarctica, using metagenomics. Half of the assembled metagenomes cluster with those in the viral family Microviridae (n = 7), and the rest with unclassified circular replication associated protein (Rep)-encoding single-stranded (CRESS) DNA viruses (n = 7). An additional 18 virus-like circular molecules encoding either a Rep, a capsid protein gene, or other unidentified but viral-like open reading frames were identified. The samples from which the genomes were identified show a strong gradient in microbial diversity and abundances, and the number of viral genomes detected in each sample mirror that gradient. Additionally, one of the CRESS genomes assembled here shares ~90% genome-wide pairwise identity with a virus identified from a freshwater pond on the McMurdo Ice Shelf (Antarctica). Otherwise, the similarity of these viruses to those previously identified is relatively low. Together, these patterns are consistent with the presence of a unique regional virome present in fresh water host populations of the McMurdo Dry Valley region.

Highlights

Viruses influence ecosystems worldwide in many ways such as by modulating microbial population size, diversity, and metabolic outputs [1,2,3,4,5]
We present the first description of single-stranded DNA (ssDNA) viruses from Antarctic cryoconite holes
The 18the viral-like circular molecules identified that cells) microviruses infect bacteria

Summary

Introduction

Viruses influence ecosystems worldwide in many ways such as by modulating microbial population size, diversity, and metabolic outputs [1,2,3,4,5]. Viruses may exert particular selection pressure and contribute to shaping the microbial Viruses may exert particular selection pressure and contribute to shaping the microbial communities of cryoconite holes [6], some of the most extreme polar freshwater ecosystems. Communities of cryoconite holes [6], some of the most extreme polar freshwater ecosystems. The sediment typically contains bacteria, algae, fungi, and microscopic animals microscopic animals such as tardigrades and bdelloid rotifers [10,15] that are active when the holes such as tardigrades and bdelloid rotifers [10,15] that are active when the holes are melted [16], often are melted [16], often becoming net photosynthetic communities [17]. Cryoconite holes can cover 0.1%–10% of the snow-free

Methods

Results

Conclusion