title: Genome sequencing of two Neorhizobium galegae strains reveals a noeT gene responsible for the unusual acetylation of the nodulation factors.
abstract: BACKGROUND
  The species Neorhizobium galegae comprises two symbiovars that induce nodules on Galega plants. Strains of both symbiovars, orientalis and officinalis, induce nodules on the same plant species, but fix nitrogen only in their own host species. The mechanism behind this strict host specificity is not yet known. In this study, genome sequences of representatives of the two symbiovars were produced, providing new material for studying properties of N. galegae, with a special interest in genomic differences that may play a role in host specificity.
  
  
  RESULTS
  The genome sequences confirmed that the two representative strains are much alike at a whole-genome level. Analysis of orthologous genes showed that N. galegae has a higher number of orthologs shared with Rhizobium than with Agrobacterium. The symbiosis plasmid of strain HAMBI 1141 was shown to transfer by conjugation under optimal conditions. In addition, both sequenced strains have an acetyltransferase gene which was shown to modify the Nod factor on the residue adjacent to the non-reducing-terminal residue. The working hypothesis that this gene is of major importance in directing host specificity of N. galegae could not, however, be confirmed.
  
  
  CONCLUSIONS
  Strains of N. galegae have many genes differentiating them from strains of Agrobacterium, Rhizobium and Sinorhizobium. However, the mechanism behind their ecological difference is not evident. Although the final determinant for the strict host specificity of N. galegae remains to be identified, the gene responsible for the species-specific acetylation of the Nod factors was identified in this study. We propose the name noeT for this gene to reflect its role in symbiosis.
authors.forename: Janina
authors.initials: J
authors.lastname: Österman
authors.forename: Joanne
authors.initials: J
authors.lastname: Marsh
authors.forename: Pia K
authors.initials: PK
authors.lastname: Laine
authors.forename: Zhen
authors.initials: Z
authors.lastname: Zeng
authors.forename: Edward
authors.initials: E
authors.lastname: Alatalo
authors.forename: John T
authors.initials: JT
authors.lastname: Sullivan
authors.forename: J Peter W
authors.initials: JP
authors.lastname: Young
authors.forename: Jane
authors.initials: J
authors.lastname: Thomas-Oates
authors.forename: Lars
authors.initials: L
authors.lastname: Paulin
authors.affiliation: Department of Food and Environmental Sciences, University of Helsinki, Viikinkaari 9, 00790 Helsinki, Finland. kristina.lindstrom@helsinki.fi.
authors.forename: Kristina
authors.initials: K
authors.lastname: Lindström
mesh_terms: D000107:Acetylation; D001426:Bacterial Proteins / Q000235:genetics* / Q000378:metabolism*; D019295:Computational Biology; D023061:Gene Order; D014644:Genetic Variation; D016680:Genome, Bacterial; D023281:Genomics; D059014:High-Throughput Nucleotide Sequencing; D008070:Lipopolysaccharides / Q000096:biosynthesis; D008969:Molecular Sequence Data; D012230:Rhizobiaceae / Q000235:genetics* / Q000378:metabolism*; D013559:Symbiosis / Q000235:genetics
chemical_list: D001426:Bacterial Proteins; D008070:Lipopolysaccharides