Associate Professor Ulrike Kappler

Associate Professor

School of Chemistry and Molecular Biosciences
Faculty of Science
+61 7 336 52978


I am interested in how microorganisms from diverse environments use metal-containing enzymes to convert toxic sulfur compounds into less harmful substrances

Sulfur compounds are essential for life on earth and fulfill many important functions in living cells, but at the same time many of these compounds are toxic due to their high reactivity. We are studying the different mechanisms that bacteria have developed to cope with exposure to such sulfur compounds....

For more information about this area, please see my Research Interests…

Research Interests

  • Sulfite oxidizing enzymes - what makes them indispensable for living cells?
    Sulfite oxidizing enzymes are found in almost all types of living cells, and especially bacteria are known to harbour a great variety of these enzymes. However, it is unknown what the metabolic role of sulfite oxidation is. We are investigating the diversity of these enzymes, the reactions catalyzed by the three structurally distinct known types of these enzymes with a view to uncovering the role of these evolutionarily old enzymes for cellular function.
  • Bacterial sulfur compound oxidation
    Energy generation from inorganic compounds, including inorganic forms of sulfur, is one of the special properties of certain bacteria. This process contributes significantly to the biogeochemical sulfur cycle, to the bioavailability of sulfur for plant growth in soils and to the detoxification of various volatile sulfur compounds, some of which are known to be climate active. We are interesting in investigating the metabolic pathways and enzymes involved in these processes, as well as their regulation in response to changing environmental conditions
  • Sulfur oxidizing extremophiles and biotechnological applications
    Alkaliphilic sulfur oxidizing bacteria have only been discovered in the last decade, and they have a unique potential for use in biotechnological applications designed to remediate sulfur pollution in waste streams and biogas. Many of the volatile sulfur compounds that are common pollutants in industrial and municipal waste as well as by-products of biogas manufacturing processes show increased solubility at the high pH values at which these bacteria thrive. Following chemical stripping of the volatile compounds from e.g. gases, the bacteria can be used to transform them into insoluble, biogenic sulfur, which can then be removed from the process.
  • Metalloenzymes and bacterial pathogenesis
    Metalloenzymes are involved in key energy-generating processes in living cells, and they contribute significantly to the adaptation of microorganisms to different environmental conditions. This project investigates how respiratory enzymes can aid pathogens in colonizing specific niches in the host and how these enzymes might be exploited as future drug targets.
  • Molecular basis for the oxidation of sulfite in bacterial sulfite dehydrogenases
    We have purified the first confirmed bacterial sulfite dehydrogenase fom Starkeya novella and have shown that it contains heme c and molybdenum. It also is structurally different from the well studied mammalian and avian sulfite oxidases: While having similar catalytic parameters, initial spectroscopic studies have shown that the reaction centre of the bacterial sulfite dehydrogenase is different from that of the sulfite oxidases. Using a variety of biochemical and spectroscopic techniques we are currently trying to elucidate the molecular processes underlying these differences. To make the enzyme more accessible to e.g. site-directed mutagenesis, a protein expression system that uses Rhodobacter capsulatus as the host has been successfully developed. A crystal structure of the enzyme (collaboration with S Bailey) will aid the understanding of the processes involved and in selecting targets for site-directed mutagenesis.


  • Graduate Certificate in Education, The University of Queensland
  • Doctorate, University of Bonn
  • Diploma of Biology, University of Bonn


View all Publications


  • Doctor Philosophy

  • Doctor Philosophy

  • Doctor Philosophy

View all Supervision


Book Chapter

  • West, J., Veenstra, A., Kappler, U., Pedwell, R., Cheung, S., O'Sullivan, L. and Rowland, S. (2019). Chapter 3: implementing an ALURE. In Susan Rowland, Gwendolyn Lawrie and Rhianna Pedwell (Ed.), Engaging undergraduate students in authentic science research: a large-scale approach (pp. 15-22) Hammondville, NSW Australia: Higher Education Research and Development Society of Australasia.

  • Kappler, Ulrike and Schwarz, Guenter (2017). The Sulfite Oxidase Family of Molybdenum Enzymes. In Hille, R., Schulzke, C. and Kirk, M. L. (Ed.), Molybdenum and tungsten enzymes : biochemistry (pp. 240-273) Cambridge, UK: Royal Society of Chemistry.

  • Kappler, Ulrike and Schwarz, Guenter (2017). The sulfite oxidase family of molybdenum enzymes. In Russ Hille, Carola Schulzke and Martin L. Kirk (Ed.), Molybdenum and tungsten enzymes: biochemistry (pp. 240-273) Cambridge, United Kingdom: Royal Society of Chemistry. doi:10.1039/9781782623915-00240

  • Kappler, Ulrike and Schäfer, Hendrik (2014). Transformations of dimethylsulfide. In The Metal-Driven Biogeochemistry of Gaseous Compounds in the Environment (pp. 279-313) Hoboken, NJ United States: John Wiley & Sons. doi:10.1007/978-94-017-9269-1_11

  • Kappler, Ulrike and Schäfer, Hendrik (2014). Transformations of dimethylsulfide. In Peter M.H. Kroneck and Martha E. Sosa Torres (Ed.), The Metal-Driven Biogeochemistry of Gaseous Compounds in the Environment (pp. 279-313) Hoboken, NJ United States: John Wiley and Sons Inc. doi:10.1007/978-94-017-9269-1_11

  • Kappler, U. (2008). Bacterial Sulfite-Oxidizing Enzymes - enzymes for Chemolithotrophs Only?. In Dahl, C. and Friedrich, C. (Ed.), Microbial Sulfur Metabolism (pp. 151-166) Berlin: Springer-Verlag.

  • Hurse, T. J., Kappler, U. and Keller, J. (2008). Using anoxygenic photosynthetic bacteria for the removal of sulfide from wastewater. In Hell, R., Dahl, C., Knaff, D. and Leustek, T. (Ed.), Sulfur Metabolism in Phototrophic Organisms 1st ed. (pp. 437-460) The Netherlands: Springer.

  • McEwan, A. G., Kappler, U. and Mc Devitt, C. (2004). Microbial molybdenum-containing enzymes in respiration: Structural and functional aspects. In D. Zannoni (Ed.), Respiration in Archaea and Bacteria 1st ed. (pp. 176-202) Dordrecht, Netherlands: Kluwer.

  • Kappler, Ulrike and Maher, Megan J. (2004). SoxAX Cytochromes. In Encyclopedia of Inorganic and Bioinorganic Chemistry (pp. 1-11) Chichester, United Kingdom: John Wiley & Sons. doi:10.1002/9781119951438.eibc2169

Journal Article

Conference Publication

Grants (Administered at UQ)

PhD and MPhil Supervision

Current Supervision

  • Doctor Philosophy — Principal Advisor

    Other advisors:

  • Doctor Philosophy — Principal Advisor

    Other advisors:

  • Doctor Philosophy — Principal Advisor

    Other advisors:

  • Doctor Philosophy — Associate Advisor

    Other advisors:

Completed Supervision