Archives of Microbiology

, Volume 171, Issue 4, pp 219–229 | Cite as

Thermodynamic aspects of energy conservation by chemolithotrophic sulfur bacteria in relation to the sulfur oxidation pathways

  • Donovan P. Kelly


The free-energy data on which assessments of the autotrophic growth efficiencies of chemolithotrophic bacteria are commonly based have been reevaluated and new values have been calculated. It has been concluded that many earlier calculations are in error and that many values previously reported in the literature are overestimates of efficiency. A problem posed by the chemolithotrophic sulfur-oxidizing bacteria is the elucidation of the mechanism by which elemental sulfur and the sulfane-sulfur (-S-) of the thionic acids are converted to sulfite. Even after decades of studies on sulfur oxidation by these bacteria, this problem has not been fully resolved although it is widely thought that conversion of sulfur to sulfite is brought about by an oxygenase. The biochemically feasible mechanisms by which sulfur and “sulfane” oxidation to sulfite might occur are reviewed. The possible insight afforded by chemical thermodynamics into the most likely mechanisms for oxidation to sulfate in relation to the efficiency of energy conservation is discussed. Energetic calculations and growth yield data indicate that the energy-yielding oxidation of sulfur and “sulfane” to sulfite, either coupled to energy-conserving electron transport or catalyzed by an oxygenase, could explain divergent growth yields among different sulfur-chemolithotrophs.

Key words Chemolithotrophic sulfur oxidation Sulfur oxygenase Energy conservation Thermodynamics Growth yields Thiobacillus Archaea 


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Copyright information

© Springer-Verlag Berlin Heidelberg 1999

Authors and Affiliations

  • Donovan P. Kelly
    • 1
  1. 1.Department of Biological Sciences, University of Warwick, Coventry CV4 7AL, UK e-mail: Tel. +44-1203-572907; Fax +44-1203-523701GB

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