BACKGROUND : The Antarctic continent is considered the coldest and driest place on earth with simple ecosystems,
devoid of higher plants. Soils in the ice-free regions of Antarctica are known to harbor a wide range of
microorganisms from primary producers to grazers, yet their ecology and particularly the role of viruses is
poorly understood. In this study, we examined the virus community structures of 14 soil samples from the
Mackay Glacier region.
METHODS : Viral communities were extracted from soil and the dsDNA was extracted, amplified using single-primer
amplification, and sequenced using the Ion Torrent Proton platform. Metadata on soil physico-chemistry was collected
from all sites. Both read and contig datasets were analyzed with reference-independent and reference-dependent
methods to assess viral community structures and the influence of environmental parameters on their distribution.
RESULTS : We observed a high heterogeneity in virus signatures, independent of geographical proximity. Tailed
bacteriophages were dominant in all samples, but the incidences of the affiliated families Siphoviridae and
Myoviridae were inversely correlated, suggesting direct competition for hosts. Viruses of the families Phycodnaviridae
and Mimiviridae were present at significant levels in high-diversity soil samples and were found to co-occur, implying
little competition between them. Combinations of soil factors, including pH, calcium content, and site altitude, were
found to be the main drivers of viral community structure.
CONCLUSIONS : The pattern of viral community structure with higher levels of diversity at lower altitude and pH,
and co-occurring viral families, suggests that these cold desert soil viruses interact with each other, the host,
and the environment in an intricate manner, playing a potentially crucial role in maintaining host diversity and
functioning of the microbial ecosystem in the extreme environments of Antarctic soil.