Title

Sulfidogenesis from sulfonates: Anaerobic sulfonate dissimilation by sulfate-reducing bacteria and Desulfitobacterium spp.

Date of Completion

January 1998

Keywords

Biology, Microbiology

Degree

Ph.D.

Abstract

Sulfidogenesis from anaerobic bacterial dissimilation of sulfonates have been demonstrated. A sulfate-reducing bacterium (SRB), Desulfovibrio desulfuricans strain IC1 was isolated with 2-hydroxethanesulfonate (isethionate) as terminal electron acceptor (TEA). Alanine-3-sulfonate (cysteate) could replace isethionate as TEA but other aliphatic, aromatic and complex sulfonates could not. Some SRB (e.g. Desulfomicrobium norvegicum and Desulfobacterium autotrophicum) but not all tested could use specific sulfonates as TEA. ^ Results from studies done with strain IC1 suggested that the initial step of isethionate reduction is a reductive cleavage of the carbon-sulfur bond releasing sulfite which is then reduced to sulfide. Also, some classical inhibitors used to stop growth of SRB allow growth of strain IC1 with isethionate but not sulfate as TEA. ^ Another group of bacteria (Desulfitobacterium spp.) able to reduce the sulfur oxyanions sulfite or thiosulfate but not sulfate have also been shown to grow with isethionate and cysteate as TEA; sulfidogenesis resulted from growth. Similar to the SRB, only some had the ability to utilize sulfonates and not all sulfonates tested could support growth. ^ Both SRB and Desulfitobacterium spp. able to grow with isethionate produced acetate and sulfide as end-products and synthesized a unique 97 kDa polypeptide suggesting that the pathways for isethionate reduction are similar if not the same. ^ A novel and morphologically unusual marine SRB was isolated that was able to grow with 2-aminoethanesulfonate (taurine) as sole carbon, energy and nitrogen source; sulfide was produced as a result of growth. Other sulfonates tested as TEA or sole sources of carbon and energy did not support growth of this bacterium. During taurine fermentation, this bacterium accumulated polyhydroxybutyrate (PHB) in quantities significantly higher than that during growth with malate + sulfate as electron donor and TEA respectively, suggesting that some of taurine's carbon was used in PHB synthesis. ^ This studies conducted here reveal an increasing number of bacterial genera able to dissimilate sulfonates under strictly anaerobic conditions for growth. This ability not only includes sulfonates as a new and significant source of sulfide in the environment but also reveals potentially novel pathways and enzymes involved in anaerobic sulfonate dissimilation. ^