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Research Article

Genome Sequence of Brucella abortus Vaccine Strain S19 Compared to Virulent Strains Yields Candidate Virulence Genes

  • Oswald R. Crasta mail,

    ocrasta@vbi.vt.edu

    Affiliation: Virginia Bioinformatics Institute, Virginia Tech, Blacksburg, Virginia, United States of America

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  • Otto Folkerts,

    Affiliation: Virginia Bioinformatics Institute, Virginia Tech, Blacksburg, Virginia, United States of America

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  • Zhangjun Fei,

    Affiliation: Virginia Bioinformatics Institute, Virginia Tech, Blacksburg, Virginia, United States of America

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  • Shrinivasrao P. Mane,

    Affiliation: Virginia Bioinformatics Institute, Virginia Tech, Blacksburg, Virginia, United States of America

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  • Clive Evans,

    Affiliation: Virginia Bioinformatics Institute, Virginia Tech, Blacksburg, Virginia, United States of America

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  • Susan Martino-Catt,

    Affiliation: Virginia Bioinformatics Institute, Virginia Tech, Blacksburg, Virginia, United States of America

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  • Betsy Bricker,

    Affiliation: National Animal Disease Center, Ames, Iowa, United States of America

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  • GongXin Yu,

    Affiliation: Virginia Bioinformatics Institute, Virginia Tech, Blacksburg, Virginia, United States of America

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  • Lei Du,

    Affiliation: 454 Life Sciences, Branford, Connecticut, United States of America

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  • Bruno W. Sobral

    Affiliation: Virginia Bioinformatics Institute, Virginia Tech, Blacksburg, Virginia, United States of America

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  • Published: May 14, 2008
  • DOI: 10.1371/journal.pone.0002193
  • Published in PLOS ONE

Reader Comments (2)

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Referee Comments: Referee 1

Posted by PLoS_ONE_Group on 19 May 2008 at 18:54 GMT

Referee 1's Review:

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N.B. These are the comments made by the referee when reviewing an earlier version of this paper. Prior to publication, the manuscript has been revised in light of these comments and to address other editorial requirements.
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The manuscript by Crasta et al describes the complete genome sequence of Brucella abortus strain 19, a live attenuated vaccine strain developed in the 1950s whose use has been instrumental in the control of bovine brucellosis in many countries in the world, including the US. While there are now 5 complete Brucella genomes available in Genbank, including two B. abortus strains, the novelty of this study is the first use of pyrosequencing and the opportunity to compare the sequence of an attenuated strain (the genetic basis is unknown) with that of fully virulent strains.

The general results, showing that S19 is almost identical to the virulent B. abortus strains is far from surprising, but this did allow the authors to identify a number of differences that may be related to the attenuation of S19.

The disappointing aspect of the manuscript is the complete lack of any biological investigation. The authors highlight a series of major differences in an autotransporter, and hint that this may be responsible for host specificity. The authors do not, however, provide any evidence that these differences, or even this protein, play a role in virulence. It would be easy to create a mutant, test its virulence and then test the ability of the different alleles to complement the mutant.
The authors should, however, also test whether the different variants are actually expressed in the different strains cited.

Similar comments can be made for the carboxyl transferase encoding locus (is S19 LPS any different form that of the virulent strains?), the IclR regulator (changes in transcription patterns; microarrays are available) and the DedA protein (what is the possible role of selinite uptake in virulence?), do the predicted erythritol transporters actually do this?

There is also a table with a list of the genes affected by SNPs. There is no discussion of this data with respect to genes known to play a role in bacterial virulence (aroA, one of the first in the list is a good example) or indications as to whether any of these genes have been identified as playing a role in Brucella virulence in previous studies.