Abstract
BackgroundThe Arctic and Antarctic are the two most geographically distant bioregions on earth. Recent sampling efforts and following metagenomics have shed light on the global ocean microbial diversity and function, yet the microbiota of polar regions has not been included in such global analyses.ResultsHere a metagenomic study of seawater samples (n = 60) collected from different depths at 28 locations in the Arctic and Antarctic zones was performed, together with metagenomes from the Tara Oceans. More than 7500 (19%) polar seawater-derived operational taxonomic units could not be identified in the Tara Oceans datasets, and more than 3,900,000 protein-coding gene orthologs had no hits in the Ocean Microbial Reference Gene Catalog. Analysis of 214 metagenome assembled genomes (MAGs) recovered from the polar seawater microbiomes, revealed strains that are prevalent in the polar regions while nearly undetectable in temperate seawater. Metabolic pathway reconstruction for these microbes suggested versatility for saccharide and lipids biosynthesis, nitrate and sulfate reduction, and CO2 fixation. Comparison between the Arctic and Antarctic microbiomes revealed that antibiotic resistance genes were enriched in the Arctic while functions like DNA recombination were enriched in the Antarctic.ConclusionsOur data highlight the occurrence of dominant and locally enriched microbes in the Arctic and Antarctic seawater with unique functional traits for environmental adaption, and provide a foundation for analyzing the global ocean microbiome in a more complete perspective.AHVueNJk6Ao36i6e4f9DMcVideo abstract.
Highlights
Recent advances in molecular ecological techniques, such as metagenomics, have enabled a more efficient pathway to address the taxonomic and functional composition of marine microbiota, including the free-living bacterioplankton [1,2,3], the sediment-dwelling microbes [4,5,6], the surfaceattached biofilms [7,8,9], and the animal-associated symbionts [10,11,12]
The aim of the present study is to address the following questions: (i) how does endemism in polar regions compare with elsewhere in the world; (ii) what are the specific functions of the polar microbiota, and how do these functions contribute to environmental adaptation
60 metagenomes were obtained after Illumina sequencing. 16S rRNA gene sequences were extracted from the metagenomes for analysis and are subsequently referred to as 16S miTags
Summary
Pursuing the goal characterizing the global seawater microbiota, the Tara Oceans expedition collected seawater samples from 68 locations, representing all main oceanic regions, and performed metagenomics to study the structure and function of the global ocean microbiota [1]. Global ocean microbial diversity has been systematically investigated, and found to consist of more than 35,000 microbial “species” [1]. One shortcoming of this holistic global ocean study is that no Arctic samples and only five Antarctic samples were included. Recent sampling efforts and following metagenomics have shed light on the global ocean microbial diversity and function, yet the microbiota of polar regions has not been included in such global analyses
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