Journal Article

Predominant archaea in marine sediments degrade detrital proteins

Richter, Michael, Lever, Mark A., Petersen, Dorthe G., Lenk, Sabine, Steen, Andrew D., Kleindienst, Sara, Stepanauskas, Ramunas, Schramm, Andreas, Lloyd, Karen G., Jørgensen, Bo Barker, Schreiber, Lars, Kjeldsen, Kasper U.

2013

Overview

Miscellaneous crenarchaeotal group (MCG) and marine benthic group-D (MBG-D) are among the most numerous archaea in sea-floor sediments; single-cell genomics reveals that these archaea belong to new branches of the archaeal tree and probably have a role in protein remineralization in anoxic marine sediments. Marine archaeans as protein recyclers Sediments on the sea floor are home to almost half of the microorganisms in the ocean, including a large number of Archaea that have not been cultured in the laboratory. Here Karen Lloyd et al . identify uncultured miscellaneous crenarchaeotal group (MCG) and marine benthic group-D (MBG-D) organisms as the predominant archaeans in sediments. Single-cell genomic analysis of four different cell types indicates that they belong to new branches of the archaeal tree. All cells tested encode extracellular protein-degrading enzymes, pointing to a possible role in protein remineralization in anoxic marine sediments. Half of the microbial cells in the Earth’s oceans are found in sediments 1 . Many of these cells are members of the Archaea 2 , single-celled prokaryotes in a domain of life separate from Bacteria and Eukaryota. However, most of these archaea lack cultured representatives, leaving their physiologies and placement on the tree of life uncertain. Here we show that the uncultured miscellaneous crenarchaeotal group (MCG) and marine benthic group-D (MBG-D) are among the most numerous archaea in the marine sub-sea floor. Single-cell genomic sequencing of one cell of MCG and three cells of MBG-D indicated that they form new branches basal to the archaeal phyla Thaumarchaeota 3 and Aigarchaeota 4 , for MCG, and the order Thermoplasmatales, for MBG-D. All four cells encoded extracellular protein-degrading enzymes such as gingipain and clostripain that are known to be effective in environments chemically similar to marine sediments. Furthermore, we found these two types of peptidase to be abundant and active in marine sediments, indicating that uncultured archaea may have a previously undiscovered role in protein remineralization in anoxic marine sediments.

• Publisher: Nature Publishing Group UK,Nature Publishing Group
• Subject: 631/326/171/1878 / 704/158/855 / Adhesins, Bacterial - metabolism / Amino acids / Animal, plant and microbial ecology / Archaea - classification / Archaea - enzymology / Archaea - genetics / Archaea - metabolism / Archaeabacteria / Bacteria / Binding sites / Biological and medical sciences / Biological evolution / Cysteine Endopeptidases - metabolism / Environmental aspects / Fundamental and applied biological sciences. Psychology / Genes / Genetics of eukaryotes. Biological and molecular evolution / Genomes / Geologic Sediments - chemistry / Geologic Sediments - microbiology / Humanities and Social Sciences / letter / Marine Biology / Marine microbiology / Marine sediments / Microbial ecology / Microbiology / Molecular Sequence Data / multidisciplinary / Ocean floor / Oceans / Peptide Hydrolases - metabolism / Phylogeny / Proteins / Proteolysis / RNA, Ribosomal, 16S - genetics / Science / Single-Cell Analysis / Taxonomy / Various environments (extraatmospheric space, air, water)