title: Taxonomy and evolution of bacteriochlorophyll a-containing members of the OM60/NOR5 clade of marine gammaproteobacteria: description of Luminiphilus syltensis gen. nov., sp. nov., reclassification of Haliea rubra as Pseudohaliea rubra gen. nov., comb. nov., and emendation of Chromatocurvus halotolerans.
abstract: BACKGROUND
  Aerobic gammaproteobacteria affiliated to the OM60/NOR5 clade are widespread in saline environments and of ecological importance in several marine ecosystems, especially the euphotic zone of coastal areas. Within this group a close relationship between aerobic anoxygenic photoheterotrophs and non-phototrophic members has been found.
  
  
  RESULTS
  Several strains of aerobic red-pigmented bacteria affiliated to the OM60/NOR5 clade were obtained from tidal flat sediment samples at the island of Sylt (North Sea, Germany). Two of the novel isolates, Rap1red and Ivo14(T), were chosen for an analysis in detail. Strain Rap1red shared a 16S rRNA sequence identity of 99% with the type strain of Congregibacter litoralis and was genome-sequenced to reveal the extent of genetic microheterogeneity among closely related strains within this clade. In addition, a draft genome sequence was obtained from the isolate Ivo14(T), which belongs to the environmental important NOR5-1 lineage that contains so far no cultured representative with a comprehensive description. Strain Ivo14(T) was characterized using a polyphasic approach and compared with other red-pigmented members of the OM60/NOR5 clade, including Congregibacter litoralis DSM 17192(T), Haliea rubra DSM 19751(T) and Chromatocurvus halotolerans DSM 23344(T). All analyzed strains contained bacteriochlorophyll a and spirilloxanthin as photosynthetic pigments. Besides a detailed phenotypic characterization including physiological and chemotaxonomic traits, sequence information based on protein-coding genes and a comparison of draft genome data sets were used to identify possible features characteristic for distinct taxa within this clade.
  
  
  CONCLUSIONS
  Comparative sequence analyses of the pufLM genes of genome-sequenced representatives of the OM60/NOR5 clade indicated that the photosynthetic apparatus of these species was derived from a common ancestor and not acquired by multiple horizontal gene transfer from phylogenetically distant species. An affiliation of the characterized bacteriochlorophyll a-containing strains to different genera was indicated by significant phenotypic differences and pufLM nucleotide sequence identity values below 82%. The revealed high genotypic and phenotypic diversity of closely related strains within this phylogenetic group reflects a rapid evolution and frequent niche separation in the OM60/NOR5 clade, which is possibly driven by the necessities of an adaptation to oligotrophic marine habitats.
authors.affiliation: Leibniz Institute DSMZ, German Collection of Microorganisms and Cell Cultures, Inhoffenstr 7B, Braunschweig 38124, Germany. ssp@dsmz.de
authors.forename: Stefan
authors.initials: S
authors.lastname: Spring
authors.forename: Thomas
authors.initials: T
authors.lastname: Riedel
authors.forename: Cathrin
authors.initials: C
authors.lastname: Spröer
authors.forename: Shi
authors.initials: S
authors.lastname: Yan
authors.forename: Jens
authors.initials: J
authors.lastname: Harder
authors.forename: Bernhard M
authors.initials: BM
authors.lastname: Fuchs
mesh_terms: D000332:Aerobiosis; D059001:Aquatic Organisms / Q000737:chemistry / Q000145:classification* / Q000235:genetics* / Q000302:isolation & purification; D025541:Bacteriochlorophyll A / Q000032:analysis*; D016000:Cluster Analysis; D004269:DNA, Bacterial / Q000737:chemistry / Q000235:genetics; D004275:DNA, Ribosomal / Q000737:chemistry / Q000235:genetics; D020563:Gammaproteobacteria / Q000737:chemistry / Q000145:classification* / Q000235:genetics* / Q000302:isolation & purification; D014644:Genetic Variation; D005858:Germany; D053858:Metabolic Networks and Pathways / Q000235:genetics; D008969:Molecular Sequence Data; D009659:North Sea; D010788:Photosynthesis; D010802:Phylogeny; D012336:RNA, Ribosomal, 16S / Q000235:genetics; D012623:Seawater / Q000382:microbiology*; D017422:Sequence Analysis, DNA
chemical_list: D025541:Bacteriochlorophyll A; D004269:DNA, Bacterial; D004275:DNA, Ribosomal; D012336:RNA, Ribosomal, 16S