title: Poles apart: Arctic and Antarctic Octadecabacter strains share high genome plasticity and a new type of xanthorhodopsin.
abstract: The genus Octadecabacter is a member of the ubiquitous marine Roseobacter clade. The two described species of this genus, Octadecabacter arcticus and Octadecabacter antarcticus, are psychrophilic and display a bipolar distribution. Here we provide the manually annotated and finished genome sequences of the type strains O. arcticus 238 and O. antarcticus 307, isolated from sea ice of the Arctic and Antarctic, respectively. Both genomes exhibit a high genome plasticity caused by an unusually high density and diversity of transposable elements. This could explain the discrepancy between the low genome synteny and high 16S rRNA gene sequence similarity between both strains. Numerous characteristic features were identified in the Octadecabacter genomes, which show indications of horizontal gene transfer and may represent specific adaptations to the habitats of the strains. These include a gene cluster encoding the synthesis and degradation of cyanophycin in O. arcticus 238, which is absent in O. antarcticus 307 and unique among the Roseobacter clade. Furthermore, genes representing a new subgroup of xanthorhodopsins as an adaptation to icy environments are present in both Octadecabacter strains. This new xanthorhodopsin subgroup differs from the previously characterized xanthorhodopsins of Salinibacter ruber and Gloeobacter violaceus in phylogeny, biogeography and the potential to bind 4-keto-carotenoids. Biochemical characterization of the Octadecabacter xanthorhodopsins revealed that they function as light-driven proton pumps.
authors.affiliation: Department of Genomic and Applied Microbiology and Göttingen Genomics Laboratory, Institute of Microbiology and Genetics, Georg-August University of Göttingen, Göttingen, Germany.
authors.forename: John
authors.initials: J
authors.lastname: Vollmers
authors.forename: Sonja
authors.initials: S
authors.lastname: Voget
authors.forename: Sascha
authors.initials: S
authors.lastname: Dietrich
authors.forename: Kathleen
authors.initials: K
authors.lastname: Gollnow
authors.forename: Maike
authors.initials: M
authors.lastname: Smits
authors.forename: Katja
authors.initials: K
authors.lastname: Meyer
authors.forename: Thorsten
authors.initials: T
authors.lastname: Brinkhoff
authors.forename: Meinhard
authors.initials: M
authors.lastname: Simon
authors.forename: Rolf
authors.initials: R
authors.lastname: Daniel
mesh_terms: D000595:Amino Acid Sequence; D000864:Antarctic Regions; D001110:Arctic Regions; D017124:Conserved Sequence; D004251:DNA Transposable Elements; D016680:Genome, Bacterial; D054892:Metagenome; D058977:Molecular Sequence Annotation; D008969:Molecular Sequence Data; D058889:Molecular Typing; D010802:Phylogeny; D058974:Phylogeography; D012329:RNA, Bacterial / Q000235:genetics; D012336:RNA, Ribosomal, 16S / Q000235:genetics; D041902:Rhodobacteraceae / Q000145:classification / Q000235:genetics*; D025604:Rhodopsins, Microbial / Q000235:genetics*; D017422:Sequence Analysis, DNA; D026801:Synteny
chemical_list: D004251:DNA Transposable Elements; D012329:RNA, Bacterial; D012336:RNA, Ribosomal, 16S; D025604:Rhodopsins, Microbial