Times are displayed in (UTC-05:00) Central Time (US & Canada) Change

Viral community dynamics in extremely acidic volcanically-impacted lakes

Session: New Voices in Geobiology

Presenting Author:

Cassandra Skaar

Authors:

Skaar, Cassandra¹, Huff, Calyssa², Jobe, Nathaniel³, Kieft, Thomas⁴, Jones, Daniel⁵

(1) Earth and Environmental Sciences, New Mexico Institute of Mining and Technology, Socorro, NM, USA, (2) Microbiology Doctoral Training Program, University of Wisconsin-Madison, Madison, WI, USA; Biology, New Mexico Institute of Mining and Technology, Socorro, NM, USA, (3) Biological Sciences, University of North Carolina at Charlotte, Charlotte, NC, USA; Biology, New Mexico Institute of Mining and Technology, Socorro, NM, USA, (4) Biology, New Mexico Institute of Mining and Technology, Socorro, NM, USA, (5) Earth and Environmental Sciences, New Mexico Institute of Mining and Technology, Socorro, NM, USA; National Cave and Karst Research Institute, Carlsbad, NM, USA,

Abstract:

Viruses are the most abundant biological entities on Earth. Bacteriophages, viruses that infect bacteria, are ubiquitous in diverse environments but have primarily been studied in the surface ocean where they have been shown to mediate microbial turnover and affect organic carbon remineralization through viral lysis. However, bacteriophages and archaeal viruses have not been as well studied in other natural settings, particularly in extreme environments where bacteria and archaea control many important biogeochemical processes. In Valles Caldera National Preserve, NM, volcanic gasses interact with surface waters, creating extremely acidic lakes and streams. Acidophilic bacteria, archaea, and microbial eukaryotes are abundant in these environments and support extreme ecosystems through chemosynthetic and photosynthetic primary productivity. In order to evaluate the impact that viruses have on microbial community dynamics in these acidic lakes, we used meta-omics, microscopy, and 16S rRNA gene sequencing to characterize viral and microbial communities across pH gradients over two years. Cell counts showed that the ratio of virus-like particles (VLPs) to cells is lower than what has been observed in most marine and freshwater environments. A majority of the viral sequences identified through metaviromic analysis were novel, although some viral sequences were closely related to viruses that infect Acidianus and Sulfolobus, two genera of acidophilic and thermophilic archaea. Within the coassembly, Acidithiobacillus and Acidiphilium were the most abundant predicted bacterial hosts and phylum Thermoproteota was the most abundant predicted archaeal hosts. Viruses encode auxiliary metabolic genes (AMGs) predicted to contribute to sulfur metabolism and transport of cellular membrane proteins and lipids along with hydrogen ions. From these observations, we hypothesize that, when conditions become extremely acidic, viral communities follow a “piggyback the winner” dynamic where most viruses adopt a lysogenic lifestyle and integrate into the genomes of the most abundant hosts, which protects the viruses from harsh conditions and provide AMGs that benefit the host. We will discuss the implications for microbiologically-catalyzed processes including sulfide oxidation and carbon dioxide fixation across this volcanically-impacted landscape, as well as ongoing culture-based efforts in this and other acidic environments.