Microbial utilization, mobilization and uptake of elemental sulfur

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The uptake and use of elemental sulfur (S0) by microorganisms is a challenging biochemical problem because S0 is extremely hydrophobic and virtually insoluble in water. Still, it is used by a large number of chemotrophic and phototrophic sulfur bacteria. Activation, uptake and transformation of S0 in these organisms are largely unexplored. Based on our recent finding that the anoxygenic phototrophic bacterium Allochromatium vinosum can take up polymeric chain-like sulfur but not the more stable cyclo-octasulfur and using a combination of innovative methods (XANES spectroscopy, microencapsulation with nanoshells) and classical physiological and molecular genetic techniques we want to solve the following questions: Which sulfur species are taken up? Is direct cell-sulfur contact necessary for sulfur uptake and which proteins are involved in this interaction? Which mechanisms are employed by the cells for mobilization and uptake of elemental sulfur? We will concentrate on two purple sulfur bacterial model organisms: (1) A. vinosum, family Chromatiaceae, forms intracellular sulfur globules. Methods for manipulative genetics are available. (2) Halorhodospira halophila, family Ectothiorhodospiraceae, forms extracellular sulfur globules. A complete genome sequence is available facilitating proteomic studies.