Application of multilocus sequence typing to study the genetic structure of megaplasmids in medicago-nodulating rhizobia

Peter Van Berkum, Patrick Elia, Bertrand D. Eardly

Research output: Contribution to journalArticle

9 Citations (Scopus)

Abstract

A multilocus sequence typing (MLST) analysis was used to examine the genetic structure and diversity within the two large extrachromosomal replicons in Medicago-nodulating rhizobia (Sinorhizobium meliloti and Sinorhizobium medicae). The allelic diversity within these replicons was high compared to the reported diversity within the corresponding chromosomes of the same strains (P. van Berkum et al., J. Bacteriol. 188:5570-5577, 2006). Also, there was strong localized linkage disequilibrium (LD) between certain pSymA loci: e.g., nodC and nifD. Although both of these observations could be explained by positive (or diversifying) selection by plant hosts, results of tests for positive selection did not provide consistent support for this hypothesis. The strong LD observed between the nodC and nifD genes could also be explained by their close proximity on the pSymA replicón. Evidence was obtained that some nodC alleles had a history of intragenic recombination, while other alleles of this locus had a history of intergenic recombination. Both types of recombination were associated with a decline in symbiotic competence with Medicago sativa as the host plant. The combined observations of LD between the nodC and nifD genes and intragenic recombination within one of these loci indicate that the symbiotic gene region on the pSymA plasmid has evolved as a clonal segment, which has been laterally transferred within the natural populations.

Original languageEnglish (US)
Pages (from-to)3967-3977
Number of pages11
JournalApplied and environmental microbiology
Volume76
Issue number12
DOIs
StatePublished - Jun 1 2010

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Multilocus Sequence Typing
Medicago
Rhizobium
Genetic Structures
linkage disequilibrium
rhizobacterium
intragenic recombination
genetic structure
Genetic Recombination
recombination
replicon
Linkage Disequilibrium
plasmids
disequilibrium
Sinorhizobium meliloti
Replicon
loci
Sinorhizobium medicae
host plants
host plant

All Science Journal Classification (ASJC) codes

  • Biotechnology
  • Food Science
  • Applied Microbiology and Biotechnology
  • Ecology

Cite this

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abstract = "A multilocus sequence typing (MLST) analysis was used to examine the genetic structure and diversity within the two large extrachromosomal replicons in Medicago-nodulating rhizobia (Sinorhizobium meliloti and Sinorhizobium medicae). The allelic diversity within these replicons was high compared to the reported diversity within the corresponding chromosomes of the same strains (P. van Berkum et al., J. Bacteriol. 188:5570-5577, 2006). Also, there was strong localized linkage disequilibrium (LD) between certain pSymA loci: e.g., nodC and nifD. Although both of these observations could be explained by positive (or diversifying) selection by plant hosts, results of tests for positive selection did not provide consistent support for this hypothesis. The strong LD observed between the nodC and nifD genes could also be explained by their close proximity on the pSymA replic{\'o}n. Evidence was obtained that some nodC alleles had a history of intragenic recombination, while other alleles of this locus had a history of intergenic recombination. Both types of recombination were associated with a decline in symbiotic competence with Medicago sativa as the host plant. The combined observations of LD between the nodC and nifD genes and intragenic recombination within one of these loci indicate that the symbiotic gene region on the pSymA plasmid has evolved as a clonal segment, which has been laterally transferred within the natural populations.",
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Application of multilocus sequence typing to study the genetic structure of megaplasmids in medicago-nodulating rhizobia. / Van Berkum, Peter; Elia, Patrick; Eardly, Bertrand D.

In: Applied and environmental microbiology, Vol. 76, No. 12, 01.06.2010, p. 3967-3977.

Research output: Contribution to journalArticle

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