Ecogenomics and Adaptation Strategies of Southern Ocean Viral Communities

Abstract

Viruses are the most abundant biologic entities in marine systems and strongly influence the microbial community composition and diversity. However, little is known about viral communities’ adaptation and diversification in the ocean.

Viruses under the Antarctic Ice Shelf are active and potentially involved in global nutrient cycles

“…Ice drilling was performed in 2017 at site HWD-2, which is located 300 km from the RIS front. During the RIS Program, seawater samples were collected at three depths (30,180, and 330 m) below the bottom of the shelf. It is important to clarify that speci c sampling for viromics (e.g.…”

“…Beneath the RIS, prokaryoplankton were of comparable diversity and abundance, though distinct composition, relative to those in the open meso-and bathypelagic ocean [25]. To put the viroplankton RIS community into global context, we compared all the predicted viral genes against the GOV 2.0 Tara virome datasets including polar stations and Malaspina expedition data from the deep ocean [26-29], isolated viruses deposited in Genbank database, and virome datasets obtained from the Southern Ocean [30]. Half of the predicted viral genes beneath the RIS did not show any homology with viral databases, while the other half showed mostly homology with ORFs from viruses mainly obtained from polar stations (Fig.…”

“…Physical isolation and high productivity characterizes the Southern Ocean (SO), which is responsible for up to one-fth of the total carbon drawdown worldwide [33]. In the Southern Ocean, a positive selection of several viral protein clusters related to cold-shock-event responses and quorum-sensing mechanisms involved in the lysogenic-lytic cycle shift decision suggested marked temperature-driven genetic selection in the SO [34]. However, under the RIS, only 3% viruses contained integrases or were detected as prophages (Suppl Material).…”

Seasonal and Spatially Distributed Viral Metagenomes from Comau Fjord (42°S), Patagonia

“…The ocean harbors a vast viral diversity that is crucial to its functioning ( 1 , 2 ). However, our understanding of viruses in the sea is mainly based on global surveys of the open ocean ( 3 – 6 ), neglecting fjords and estuaries despite their ecological importance and the ecosystem services that they provide ( 7 ). Comau Fjord, Patagonia, is a semiclosed basin whose waters harbor open-cage aquaculture centers and are used for commercial and passenger transport routes ( 8 ).…”

Over two decades of research on the marine RNA virosphere

“…Extreme marine environments, such as deep-sea, polar, and hot regions, hydrothermal vents, and areas of high pressure or salinity, are close to the limits of life [71]. Virus communities adapt to extreme environments by skewing the coding frequencies of specific amino acid residues [72,73]. Extreme environments do not increase the mutation rate of viruses, but selection pressure from the local environment can increase the abundance of certain types of viruses [74].…”