Abstract

Salar de Huasco is a wetland in the Andes mountains, located 3800 m above sea level at the Chilean Altiplano. Here we present a study aimed at characterizing the viral fraction and the microbial communities through metagenomic analysis. Two ponds (H0 and H3) were examined in November 2015. Water samples were processed using tangential flow filtration to obtain metagenomes from which the DNA fraction of the sample was amplified and sequenced (HiSeq system, Illumina). The ponds were characterized by freshwater and the viral-like particles to picoplankton ratio was 12.1 and 2.3 for H0 and H3, respectively. A great number of unassigned viral sequences were found in H0 (55.8%) and H3 (32.8%), followed by the family Fuselloviridae 20.8% (H0) and other less relatively abundant groups such as Microviridae (H0, 11.7% and H3, 3.3%) and Inoviridae (H3, 2.7%). The dominant viral sequences in both metagenomes belong to the order Caudovirales, with Siphoviridae being the most important family, especially in H3 (32.7%). The most important bacteria phyla were Proteobacteria, Bacteroidetes and Firmicutes in both sites, followed by Cyanobacteria (H0). Genes encoding lysogenic and lytic enzymes (i.e., recombinases and integrases) were found in H0 and H3, indicating a potential for active viral replication at the time of sampling; this was supported by the presence of viral metabolic auxiliary genes at both sites (e.g., cysteine hydrolase). In total, our study indicates a great novelty of viral groups, differences in taxonomic diversity and replication pathways between sites, which contribute to a better understanding of how viruses balance the cycling of energy and matter in this extreme environment.

Highlights

  • Wetlands play an important role in many ecological contexts, including climate change, biodiversity, hydrology, and human health [1]; these ecosystems are constantly threatened by human activities [2,3]

  • We examine two viral-enriched metagenomes from freshwater ponds in a high-altitude wetland and classify DNA viruses, identify potential new bacteriophage and their putative hosts, describe genes encoding enzymes related to the lytic and lysogenic cycles, and classify auxiliary metabolic genes (AMGs) related to metabolic pathways of the biogeochemical cycles in Salar de Huasco wetland

  • Instead, during the sampling in November 2014 and March 2015, virus-like particles (VLP) (105 VLP mL−1) and picoplankton (104–105 cells mL−1) abundance was lower than the ones report here, but virus to picoplankton abundance ratio (VPR) were similar to H0 (i.e., 9.4 and 13.2 for H0 spring and H3 spring, respectively) [45]

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Summary

Introduction

Wetlands play an important role in many ecological contexts, including climate change, biodiversity, hydrology, and human health [1]; these ecosystems are constantly threatened by human activities [2,3]. Salar de Huasco is a salt-flat or Salar in local language, located in the Chilean altiplano and classified as a high-altitude wetland under the Ramsar convention since 1996 Despite this denomination, it is subjected to human impact by tourism and mining activities, underlining the importance of performing baseline studies of the natural ecology of this wetland. It is subjected to human impact by tourism and mining activities, underlining the importance of performing baseline studies of the natural ecology of this wetland This ecosystem presents a large variety of environments, from transient ponds and streams to a main lake where flamingos and llamas cohabitate among other species [5]. Final DNA concentration was measured with MaestroNano® spectrophotometer

Sequencing and in Silico Analysis
Results and Discussion
Viral Genome Composition
Functional Analysis of Viral Sequences
Conclusions
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