Dr Karrera Djoko

Research Fellow

School of Chemistry and Molecular Biosciences
Faculty of Science
k.djoko@uq.edu.au
+61 7 336 54603

Overview

The mucosal pathogens Neisseria gonorrhoeae and Escherichia coli represent two out of three ‘urgent’ threats to public health because of rising antibiotic resistance (Center for Disease Control, 2013). To better understand their virulence mechanisms, I use multidisciplinary approaches that draw on my training in bioinorganic chemistry and postdoctoral experience in molecular microbiology. Of particular focus is their ability to manage metals, particularly copper, during host-pathogen interactions. The results guide development of copper-based strategies for managing infection in a clinical setting.

RESEARCH SUMMARY

Trace nutrient metals (eg. iron, zinc, copper) are essential for the function of nearly half of all proteins in cells but they are toxic if present in excess or if found in the wrong cellular location. The battle to control metal location and availability is now recognised as a key component of host-pathogen interactions. Host immune strategies that starve invading pathogens of iron and zinc, and, conversely, bacterial mechanisms to acquire metals are well characterised. In contrast, host mechanisms that harness metals (mainly copper) to kill bacteria and the importance of copper tolerance in bacterial virulence are still emerging.

At the fundamental biochemical level, copper poisons bacteria by displacing other metal ions in metalloproteins. However, precisely which protein is targeted is not always predictable – it varies with the organism and the consequence on pathogenesis is not immediately obvious. To avoid copper stress, almost all bacterial pathogens possess inducible efflux pumps for removing copper from the cytoplasm. Apart from this central export feature, the function and organisation of bacterial copper tolerance systems are surprisingly diverse. Some pathogens possess multiple accessory proteins and genes, many with ambiguous function. In others, these additional components, including the copper sensor, are absent altogether.

Key questions that drive my research are:

1. What are the specific targets of poisoning / how does copper impact bacterial physiology?

2. How do bacteria manage the toxic effects of copper (apart from export)?

3. When/where in the host do bacterial pathogens encounter copper?

4. Can we learn from nature and develop copper as modern antibacterial therapeutics?

Qualifications

  • Doctor of Philosophy, University of Melbourne
  • Bachelor of Science, Pennsylvania State University

Publications

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Supervision

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Publications

Featured Publications

Book Chapter

  • Djoko, Karrera Y., Achard, Maud E. S. and McEwan, Alastair G. (2013). Copper in immune cells. In Valeria Culotta and Robert A. Scott (Ed.), Metals in Cells (pp. 409-420) Hoboken, New Jersey, USA: John Wiley & Sons. doi:10.1002/9781119951438

Journal Article

Conference Publication

Grants (Administered at UQ)

PhD and MPhil Supervision

Current Supervision

Completed Supervision