title: Genome organization and localization of the pufLM genes of the photosynthesis reaction center in phylogenetically diverse marine Alphaproteobacteria.
abstract: Genome organization, plasmid content and localization of the pufLM genes of the photosynthesis reaction center were studied by pulsed-field gel electrophoresis (PFGE) in marine phototrophic Alphaproteobacteria. Both anaerobic phototrophs (Rhodobacter veldkampii and Rhodobacter sphaeroides) and strictly aerobic anoxygenic phototrophs from the Roseobacter-Sulfitobacter-Silicibacter clade (Roseivivax halodurans, Roseobacter litoralis, Staleya guttiformis, Roseovarius tolerans, and five new strains isolated from dinoflagellate cultures) were investigated. The complete genome size was estimated for R. litoralis DSM6996(T) to be 4,704 kb, including three linear plasmids. All strains contained extrachromosomal elements of various conformations (linear or circular) and lengths (between 4.35 and 368 kb). In strain DFL-12, a member of a putative new genus isolated from a culture of the toxic dinoflagellate Prorocentrum lima, seven linear plasmids were found, together comprising 860 kb of genetic information. Hybridization with probes against the pufLM genes of the photosynthesis gene cluster after Southern transfer of the genomic DNAs showed these genes to be located on a linear plasmid of 91 kb in R. litoralis and on a linear plasmid of 120 kb in S. guttiformis, theoretically allowing their horizontal transfer. In all other strains, the pufLM genes were detected on the bacterial chromosome. The large number and significant size of the linear plasmids found especially in isolates from dinoflagellates might account for the metabolic versatility and presumed symbiotic association with eukaryotic hosts in these bacteria.
authors.affiliation: Deutsche Sammlung von Mikroorganismen und Zellkulturen GmbH, D-38124 Braunschweig, Germany.
authors.forename: Silke
authors.initials: S
authors.lastname: Pradella
authors.forename: Martin
authors.initials: M
authors.lastname: Allgaier
authors.forename: Christa
authors.initials: C
authors.lastname: Hoch
authors.forename: Orsola
authors.initials: O
authors.lastname: Päuker
authors.forename: Erko
authors.initials: E
authors.lastname: Stackebrandt
authors.forename: Irene
authors.initials: I
authors.lastname: Wagner-Döbler
mesh_terms: D020561:Alphaproteobacteria / Q000235:genetics* / Q000378:metabolism; D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism*; D002874:Chromosome Mapping; D016521:Electrophoresis, Gel, Pulsed-Field; D016680:Genome, Bacterial; D045342:Light-Harvesting Protein Complexes / Q000235:genetics / Q000378:metabolism*; D008969:Molecular Sequence Data; D010788:Photosynthesis; D045322:Photosynthetic Reaction Center Complex Proteins / Q000235:genetics / Q000378:metabolism*; D010802:Phylogeny; D010957:Plasmids / Q000235:genetics; D015183:Restriction Mapping; D012242:Rhodobacter sphaeroides; D041904:Roseobacter / Q000235:genetics / Q000378:metabolism; D017422:Sequence Analysis, DNA
chemical_list: D001426:Bacterial Proteins; D045342:Light-Harvesting Protein Complexes; D045322:Photosynthetic Reaction Center Complex Proteins; C096433:PufL protein, Bacteria; C098543:PufM protein, Bacteria