Insights of Phage-Host Interaction in Hypersaline Ecosystem through Metagenomics Analyses.

Amir Mohaghegh Motlagh,Sherwood R. Casjens,Bas E. Dutilh,Ramesh K. Goel,Felipe H. Coutinho,Ananda S. Bhattacharjee

doi:10.3389/fmicb.2017.00352

Abstract

Bacteriophages, as the most abundant biological entities on Earth, place significant predation pressure on their hosts. This pressure plays a critical role in the evolution, diversity, and abundance of bacteria. In addition, phages modulate the genetic diversity of prokaryotic communities through the transfer of auxiliary metabolic genes. Various studies have been conducted in diverse ecosystems to understand phage-host interactions and their effects on prokaryote metabolism and community composition. However, hypersaline environments remain among the least studied ecosystems and the interaction between the phages and prokaryotes in these habitats is poorly understood. This study begins to fill this knowledge gap by analyzing bacteriophage-host interactions in the Great Salt Lake, the largest prehistoric hypersaline lake in the Western Hemisphere. Our metagenomics analyses allowed us to comprehensively identify the bacterial and phage communities with Proteobacteria, Firmicutes, and Bacteroidetes as the most dominant bacterial species and Siphoviridae, Myoviridae, and Podoviridae as the most dominant viral families found in the metagenomic sequences. We also characterized interactions between the phage and prokaryotic communities of Great Salt Lake and determined how these interactions possibly influence the community diversity, structure, and biogeochemical cycles. In addition, presence of prophages and their interaction with the prokaryotic host was studied and showed the possibility of prophage induction and subsequent infection of prokaryotic community present in the Great Salt Lake environment under different environmental stress factors. We found that carbon cycle was the most susceptible nutrient cycling pathways to prophage induction in the presence of environmental stresses. This study gives an enhanced snapshot of phage and prokaryote abundance and diversity as well as their interactions in a hypersaline complex ecosystem, which can pave the way for further research studies.

Highlights

Microbial communities and prokaryotes provide diverse ecosystem functions in aquatic habitats
Significantly low dissolved oxygen levels in the deep brine layer and high concentration of total phosphorus (TP) and total nitrogen (TN) make the water of the Great Salt Lake an extreme environment, which selects for a microbiota adapted to high salt concentrations
The Great Salt Lake is one of the most unique hypersaline environments on the planet and has a high diversity in bacteria and bacteriophage species, and many of the bacteria are involved in various nutrient cycles

Summary

Introduction

Microbial communities and prokaryotes provide diverse ecosystem functions in aquatic habitats. Bacteriophages outnumber prokaryotic cells in many ecosystems, exerting significant predation pressure on their hosts (Williamson et al, 2008). This pressure plays a critical role in the evolution, diversity, and abundance of prokaryotes (Stern and Sorek, 2011). Bacteriophages can influence the genetic diversity of prokaryotic communities in many different ways Phages selectively kill their hosts, often in a “kill-the-winner” dynamic (Thingstad et al, 2008) in which the most abundant members of a microbial community are the most targeted by phage infection, having their genes temporarily depleted from the genetic pool of a given habitat (Motlagh et al, 2016)

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Conclusion