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Molecular analysis of the distribution and phylogeny of the soxB gene among sulfur-oxidizing bacteria – evolution of the Sox sulfur oxidation enzyme system

Authors

  • Birte Meyer,

    1. Max-Planck-Institute for Marine Microbiology, Celsiusstrasse 1, D-28359 Bremen, Germany.
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  • Johannes F. Imhoff,

    1. Marine Microbiology, IFM-GEOMAR, Düsternbrooker Weg 20, D-24105 Kiel, Germany.
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  • Jan Kuever

    Corresponding author
    1. Max-Planck-Institute for Marine Microbiology, Celsiusstrasse 1, D-28359 Bremen, Germany.
      *E-mail kuever@mpa-bremen.de; Tel. (+49) 0421 5370870; Fax (+49) 0421 5370810.
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    • Present address: Bremen Institute for Materials Testing, Paul-Feller-Strasse 1, D-28199 Bremen, Germany.


*E-mail kuever@mpa-bremen.de; Tel. (+49) 0421 5370870; Fax (+49) 0421 5370810.

Summary

The soxB gene encodes the SoxB component of the periplasmic thiosulfate-oxidizing Sox enzyme complex, which has been proposed to be widespread among the various phylogenetic groups of sulfur-oxidizing bacteria (SOB) that convert thiosulfate to sulfate with and without the formation of sulfur globules as intermediate. Indeed, the comprehensive genetic and genomic analyses presented in the present study identified the soxB gene in 121 phylogenetically and physiologically divergent SOB, including several species for which thiosulfate utilization has not been reported yet. In first support of the previously postulated general involvement of components of the Sox enzyme complex in the thiosulfate oxidation process of sulfur-storing SOB, the soxB gene was detected in all investigated photo- and chemotrophic species that form sulfur globules during thiosulfate oxidation (Chromatiaceae, Chlorobiaceae, Ectothiorhodospiraceae, Thiothrix, Beggiatoa, Thiobacillus, invertebrate symbionts and free-living relatives). The SoxB phylogeny reflected the major 16S rRNA gene-based phylogenetic lineages of the investigated SOB, although topological discrepancies indicated several events of lateral soxB gene transfer among the SOB, e.g. its independent acquisition by the anaerobic anoxygenic phototrophic lineages from different chemotrophic donor lineages. A putative scenario for the proteobacterial origin and evolution of the Sox enzyme system in SOB is presented considering the phylogenetic, genomic (sox gene cluster composition) and geochemical data.

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