Comparative genomics of the core and accessory genomes of 48 Sinorhizobium strains comprising five genospecies

Masayuki Sugawara, Brendan Epstein, Brian Badgley, Tatsuya Unno, Lei Xu, Jennifer Reese, Prasad Gyaneshwar, Roxanne Denny, Joann Mudge, Arvind K. Bharti, Andrew D. Farmer, Gregory D. May, Jimmy E. Woodward, Claudine Medigue, David Vallenet, Aurelie Lajus, Zoe Rouy, Betsy Martinez-Vaz, Peter Tiffin, Nevin D. YoungMichael J. Sadowsky

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115 Scopus citations

Abstract

Background: The sinorhizobia are amongst the most well studied members of nitrogen-fixing root nodule bacteria and contribute substantial amounts of fixed nitrogen to the biosphere. While the alfalfa symbiont Sinorhizobium meliloti RM 1021 was one of the first rhizobial strains to be completely sequenced, little information is available about the genomes of this large and diverse species group. Results: Here we report the draft assembly and annotation of 48 strains of Sinorhizobium comprising five genospecies. While S. meliloti and S. medicae are taxonomically related, they displayed different nodulation patterns on diverse Medicago host plants, and have differences in gene content, including those involved in conjugation and organic sulfur utilization. Genes involved in Nod factor and polysaccharide biosynthesis, denitrification and type III, IV, and VI secretion systems also vary within and between species. Symbiotic phenotyping and mutational analyses indicated that some type IV secretion genes are symbiosis-related and involved in nitrogen fixation efficiency. Moreover, there is a correlation between the presence of type IV secretion systems, heme biosynthesis and microaerobic denitrification genes, and symbiotic efficiency. Conclusions: Our results suggest that each Sinorhizobium strain uses a slightly different strategy to obtain maximum compatibility with a host plant. This large genome data set provides useful information to better understand the functional features of five Sinorhizobium species, especially compatibility in legume-Sinorhizobium interactions. The diversity of genes present in the accessory genomes of members of this genus indicates that each bacterium has adopted slightly different strategies to interact with diverse plant genera and soil environments.

Original languageEnglish (US)
Article numberR17
JournalGenome biology
Volume14
Issue number2
DOIs
StatePublished - Feb 20 2013

Bibliographical note

Publisher Copyright:
© 2013 Sugawara et al.; licensee BioMed Central Ltd.

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