title: Phylogenetic analysis of psychrophilic bacteria isolated from the Japan Trench, including a description of the deep-sea species Psychrobacter pacificensis sp. nov.
abstract: Phylogenetic positions of psychrophilic bacteria isolated from the Japan Trench were determined by sequencing analysis of PCR-amplified bacterial small subunit (16S) rRNA genes. Between surface and deep-sea psychrophiles, distinct positions clearly differed within the gamma-Proteobacteria. In phylogenetic analysis using neighbour-joining, maximum-parsimony and maximum-likelihood, strains from surface seawater were inferred to be located in the Halomonas aquamarina-meridiana clade within the family Halomonadaceae. Strains from deep seawater (5000-6000 m), however, formed a novel monophyletic clade within the Moraxella-Psychrobacter branch in the family Moraxellaceae, showing separation from terrestrial and Antarctic relatives. These deep-sea strains were also discriminated from other known Psychrobacter species in phenotype, e.g. limited growth in the absence of NaCl (optimum at about 3% NaCl), positive urease activity, acid production from xylose and arabinose, and the presence of multiple fimbriae. DNA relatedness values among six deep-sea strains were > 85% in DNA-DNA hybridization experiments and > 98% in aligned 16S rDNA sequences. From this evidence, a new species, Psychrobacter pacificensis, is proposed for these deep-sea psychrophiles; the type strain of Psychrobacter pacificensis is strain NIBH P2K6T (= IFO 16270T). Occurrence of psychrobacters in cold Japan Trench deep seawater and at the Antarctic sea surface suggests that deep-sea bacterial habitation and evolution have been mediated by global deep-ocean circulation linked to the sinking of cooled seawater in polar regions.
authors.forename: A
authors.initials: A
authors.lastname: Maruyama
authors.forename: D
authors.initials: D
authors.lastname: Honda
authors.forename: H
authors.initials: H
authors.lastname: Yamamoto
authors.forename: K
authors.initials: K
authors.lastname: Kitamura
authors.forename: T
authors.initials: T
authors.lastname: Higashihara
mesh_terms: D003080:Cold Temperature; D004269:DNA, Bacterial / Q000235:genetics; D004275:DNA, Ribosomal / Q000235:genetics; D020563:Gammaproteobacteria / Q000145:classification* / Q000235:genetics / Q000302:isolation & purification / Q000502:physiology; D020632:Halomonas / Q000145:classification / Q000235:genetics / Q000302:isolation & purification; D007564:Japan; D009016:Moraxella / Q000145:classification / Q000235:genetics / Q000302:isolation & purification; D009068:Movement; D009693:Nucleic Acid Hybridization; D010641:Phenotype; D010802:Phylogeny; D012336:RNA, Ribosomal, 16S / Q000235:genetics; D012623:Seawater / Q000382:microbiology*; D017422:Sequence Analysis, DNA; D014871:Water Microbiology
chemical_list: D004269:DNA, Bacterial; D004275:DNA, Ribosomal; D012336:RNA, Ribosomal, 16S