title: Strangers in the archaeal world: osmostress-responsive biosynthesis of ectoine and hydroxyectoine by the marine thaumarchaeon Nitrosopumilus maritimus.
abstract: Ectoine and hydroxyectoine are compatible solutes widely synthesized by members of the Bacteria to cope with high osmolarity surroundings. Inspection of 557 archaeal genomes revealed that only 12 strains affiliated with the Nitrosopumilus, Methanothrix or Methanobacterium genera harbour ectoine/hydroxyectoine gene clusters. Phylogenetic considerations suggest that these Archaea have acquired these genes through horizontal gene transfer events. Using the Thaumarchaeon 'Candidatus Nitrosopumilus maritimus' as an example, we demonstrate that the transcription of its ectABCD genes is osmotically induced and functional since it leads to the production of both ectoine and hydroxyectoine. The ectoine synthase and the ectoine hydroxylase were biochemically characterized, and their properties resemble those of their counterparts from Bacteria. Transcriptional analysis of osmotically stressed 'Ca. N. maritimus' cells demonstrated that they possess an ectoine/hydroxyectoine gene cluster (hyp-ectABCD-mscS) different from those recognized previously since it contains a gene for an MscS-type mechanosensitive channel. Complementation experiments with an Escherichia coli mutant lacking all known mechanosensitive channel proteins demonstrated that the (Nm)MscS protein is functional. Hence, 'Ca. N. maritimus' cells cope with high salinity not only through enhanced synthesis of osmostress-protective ectoines but they already prepare themselves simultaneously for an eventually occurring osmotic down-shock by enhancing the production of a safety-valve (NmMscS).
authors.affiliation: Laboratory for Molecular Microbiology, Department of Biology, Philipps-University, Karl-von-Frisch Str. 8, D-35043, Marburg, Germany.
authors.forename: Nils
authors.initials: N
authors.lastname: Widderich
authors.affiliation: Laboratory for Molecular Microbiology, Department of Biology, Philipps-University, Karl-von-Frisch Str. 8, D-35043, Marburg, Germany.
authors.forename: Laura
authors.initials: L
authors.lastname: Czech
authors.affiliation: Organic Geochemistry Group, MARUM - Center for Marine Environmental Sciences, University of Bremen, PO Box 330 440, D-28334, Bremen, Germany.
authors.forename: Felix J
authors.initials: FJ
authors.lastname: Elling
authors.affiliation: Organic Geochemistry Group, MARUM - Center for Marine Environmental Sciences, University of Bremen, PO Box 330 440, D-28334, Bremen, Germany.
authors.forename: Martin
authors.initials: M
authors.lastname: Könneke
authors.affiliation: Laboratory for Molecular Microbiology, Department of Biology, Philipps-University, Karl-von-Frisch Str. 8, D-35043, Marburg, Germany.|LOEWE-Center for Synthetic Microbiology, Philipps-University Marburg, Hans-Meerwein-Str. 6, D-35043, Marburg, Germany.
authors.forename: Nadine
authors.initials: N
authors.lastname: Stöveken
authors.affiliation: Laboratory for Molecular Microbiology, Department of Biology, Philipps-University, Karl-von-Frisch Str. 8, D-35043, Marburg, Germany.
authors.forename: Marco
authors.initials: M
authors.lastname: Pittelkow
authors.affiliation: Kekulé-Institut for Organic Chemistry and Biochemistry, Friedrich-Wilhelms-University Bonn, Gerhard-Domagk Str. 1, D-53121, Bonn, Germany.|Institute of Organic Chemistry, TU Braunschweig, Hagenring 30, D-38106, Braunschweig, Germany.
authors.forename: Ramona
authors.initials: R
authors.lastname: Riclea
authors.affiliation: Kekulé-Institut for Organic Chemistry and Biochemistry, Friedrich-Wilhelms-University Bonn, Gerhard-Domagk Str. 1, D-53121, Bonn, Germany.|Institute of Organic Chemistry, TU Braunschweig, Hagenring 30, D-38106, Braunschweig, Germany.
authors.forename: Jeroen S
authors.initials: JS
authors.lastname: Dickschat
authors.affiliation: Laboratory for Molecular Microbiology, Department of Biology, Philipps-University, Karl-von-Frisch Str. 8, D-35043, Marburg, Germany.|LOEWE-Center for Synthetic Microbiology, Philipps-University Marburg, Hans-Meerwein-Str. 6, D-35043, Marburg, Germany.
authors.forename: Johann
authors.initials: J
authors.lastname: Heider
authors.affiliation: Laboratory for Molecular Microbiology, Department of Biology, Philipps-University, Karl-von-Frisch Str. 8, D-35043, Marburg, Germany.|LOEWE-Center for Synthetic Microbiology, Philipps-University Marburg, Hans-Meerwein-Str. 6, D-35043, Marburg, Germany.
authors.forename: Erhard
authors.initials: E
authors.lastname: Bremer
mesh_terms: D000595:Amino Acid Sequence; D000599:Amino Acids, Diamino / Q000096:biosynthesis* / Q000235:genetics; D001105:Archaea / Q000235:genetics / Q000378:metabolism*; D004926:Escherichia coli / Q000235:genetics; D022761:Gene Transfer, Horizontal / Q000235:genetics; D006836:Hydro-Lyases / Q000235:genetics*; D008465:Mechanoreceptors / Q000378:metabolism; D006899:Mixed Function Oxygenases / Q000235:genetics; D005810:Multigene Family / Q000235:genetics; D009997:Osmotic Pressure / Q000502:physiology*; D010802:Phylogeny
chemical_list: D000599:Amino Acids, Diamino; C121557:hydroxyectoine; C045628:ectoine; D006899:Mixed Function Oxygenases; D006836:Hydro-Lyases; C106231:ectoine synthase