Abstract
BackgroundAcidithiobacillus ferrooxidans is a gamma-proteobacterium that lives at pH2 and obtains energy by the oxidation of sulfur and iron. It is used in the biomining industry for the recovery of metals and is one of the causative agents of acid mine drainage. Effective tools for the study of its genetics and physiology are not in widespread use and, despite considerable effort, an understanding of its unusual physiology remains at a rudimentary level. Nearly complete genome sequences of A. ferrooxidans are available from two public sources and we have exploited this information to reconstruct aspects of its sulfur metabolism.ResultsTwo candidate mechanisms for sulfate uptake from the environment were detected but both belong to large paralogous families of membrane transporters and their identification remains tentative. Prospective genes, pathways and regulatory mechanisms were identified that are likely to be involved in the assimilation of sulfate into cysteine and in the formation of Fe-S centers. Genes and regulatory networks were also uncovered that may link sulfur assimilation with nitrogen fixation, hydrogen utilization and sulfur reduction. Potential pathways were identified for sulfation of extracellular metabolites that may possibly be involved in cellular attachment to pyrite, sulfur and other solid substrates.ConclusionsA bioinformatic analysis of the genome sequence of A. ferrooxidans has revealed candidate genes, metabolic process and control mechanisms potentially involved in aspects of sulfur metabolism. Metabolic modeling provides an important preliminary step in understanding the unusual physiology of this extremophile especially given the severe difficulties involved in its genetic manipulation and biochemical analysis.
Highlights
Acidithiobacillus ferrooxidans is a gamma-proteobacterium that lives at pH2 and obtains energy by the oxidation of sulfur and iron
Nothing is known about the possible coordinated regulation of sulfur metabolism and hydrogen utilization and nitrogen fixation that are known from studies in other organisms to impinge upon sulfur metabolism
We posit that the preliminary metabolic model for sulfur uptake and assimilation in A. ferrooxidans presented here has permitted the capture of potentially biologically valid relations that have been highlighted for experimental validation
Summary
Acidithiobacillus ferrooxidans is a gamma-proteobacterium that lives at pH2 and obtains energy by the oxidation of sulfur and iron. Acidithiobacillus ferrooxidans is a chemolithotrophic, mesophilic, gamma-proteobacterium that lives at pH2 It is found in mine drainage and coal wastes and other acidic environments and is used extensively as part of a consortium of microorganisms for the industrial recovery of metals, such as copper and gold [1]. It can obtain all its energy and electron requirements from the oxidation of various forms of reduced sulfur and ferrous iron. Questions arise as to how membrane transport mechanisms function in A. ferrooxidans when confronted by a pH gradient that covers five logs of magnitude, especially considering that in neutrophilic organisms many of these transporters are symporters or antiporters using protons to drive uptake or discharge of metabolites
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