title: The nitrogen-fixation island insertion site is conserved in diazotrophic Pseudomonas stutzeri and Pseudomonas sp. isolated from distal and close geographical regions.
abstract: The presence of nitrogen fixers within the genus Pseudomonas has been established and so far most isolated strains are phylogenetically affiliated to Pseudomonas stutzeri. A gene ortholog neighborhood analysis of the nitrogen fixation island (NFI) in four diazotrophic P. stutzeri strains and Pseudomonas azotifigens revealed that all are flanked by genes coding for cobalamin synthase (cobS) and glutathione peroxidise (gshP). The putative NFIs lack all the features characterizing a mobilizable genomic island. Nevertheless, bioinformatic analysis P. stutzeri DSM 4166 NFI demonstrated the presence of short inverted and/or direct repeats within both flanking regions. The other P. stutzeri strains carry only one set of repeats. The genetic diversity of eleven diazotrophic Pseudomonas isolates was also investigated. Multilocus sequence typing grouped nine isolates along with P. stutzeri and two isolates are grouped in a separate clade. A Rep-PCR fingerprinting analysis grouped the eleven isolates into four distinct genotypes. We also provided evidence that the putative NFI in our diazotrophic Pseudomonas isolates is flanked by cobS and gshP genes. Furthermore, we demonstrated that the putative NFI of Pseudomonas sp. Gr65 is flanked by inverted repeats identical to those found in P. stutzeri DSM 4166 and while the other P. stutzeri isolates harbor the repeats located in the intergenic region between cobS and glutaredoxin genes as in the case of P. stutzeri A1501. Taken together these data suggest that all putative NFIs of diazotrophic Pseudomonas isolates are anchored in an intergenic region between cobS and gshP genes and their flanking regions are designated by distinct repeats patterns. Moreover, the presence of almost identical NFIs in diazotrophic Pseudomonas strains isolated from distal geographical locations around the world suggested that this horizontal gene transfer event may have taken place early in the evolution.
authors.affiliation: Department of Crop Science, Laboratory of General and Agricultural Microbiology, Agricultural University of Athens, Athens, Greece.
authors.forename: Anastasia
authors.initials: A
authors.lastname: Venieraki
authors.affiliation: Department of Crop Science, Laboratory of General and Agricultural Microbiology, Agricultural University of Athens, Athens, Greece.
authors.forename: Maria
authors.initials: M
authors.lastname: Dimou
authors.affiliation: Department of Crop Science, Laboratory of General and Agricultural Microbiology, Agricultural University of Athens, Athens, Greece.
authors.forename: Eleni
authors.initials: E
authors.lastname: Vezyri
authors.affiliation: Department of Crop Science, Laboratory of General and Agricultural Microbiology, Agricultural University of Athens, Athens, Greece.
authors.forename: Alexandros
authors.initials: A
authors.lastname: Vamvakas
authors.affiliation: Department of Crop Science, Laboratory of General and Agricultural Microbiology, Agricultural University of Athens, Athens, Greece.
authors.forename: Pagona-Artemis
authors.initials: PA
authors.lastname: Katinaki
authors.affiliation: Department of Crop Science, Laboratory of General and Agricultural Microbiology, Agricultural University of Athens, Athens, Greece.
authors.forename: Iordanis
authors.initials: I
authors.lastname: Chatzipavlidis
authors.affiliation: Department of Crop Science, Laboratory of General and Agricultural Microbiology, Agricultural University of Athens, Athens, Greece.
authors.forename: Anastasia
authors.initials: A
authors.lastname: Tampakaki
authors.affiliation: Department of Crop Science, Laboratory of General and Agricultural Microbiology, Agricultural University of Athens, Athens, Greece.
authors.forename: Panagiotis
authors.initials: P
authors.lastname: Katinakis
mesh_terms: D001426:Bacterial Proteins / Q000235:genetics; D001483:Base Sequence; D002681:China; D004269:DNA, Bacterial / Q000737:chemistry / Q000235:genetics; D019143:Evolution, Molecular; D014644:Genetic Variation; D044404:Genomic Islands / Q000235:genetics*; D005843:Geography; D005858:Germany; D006115:Greece; D008957:Models, Genetic; D008969:Molecular Sequence Data; D009586:Nitrogen Fixation / Q000235:genetics*; D010802:Phylogeny; D011549:Pseudomonas / Q000145:classification / Q000235:genetics*; D044223:Pseudomonas stutzeri / Q000235:genetics*; D012336:RNA, Ribosomal, 16S / Q000235:genetics; D012091:Repetitive Sequences, Nucleic Acid / Q000235:genetics; D017422:Sequence Analysis, DNA; D012689:Sequence Homology, Nucleic Acid; D013045:Species Specificity
chemical_list: D001426:Bacterial Proteins; D004269:DNA, Bacterial; D012336:RNA, Ribosomal, 16S