Prof. D.E. Rawlings
Prof. Rawlings is an internationally recognised leader in the field of biomining bacteria, and his research group has been studying the molecular biology of these organisms for 25 years. His long term Research Fellow, Dr Shelly Deane, is responsible for the running of the lab, supervision of projects from Hons to PhD level, and the initiation of new areas of research. In addition, the group consists of research students, Wesley Loftie-Eaton (PhD), Cristin Barnard (MSc) and Inge Laubsher (MSc), Corne Bosch (BSc Hons) and Louise Vos (BSc Hons) .
Biomining bacteria are used in the recovery of metals from ores. These bacteria have an unusual physiology in that they obtain their carbon by fixing carbon dioxide and their energy from the oxidation of either ferrous iron or reduced sulphur compounds. The sulphuric acid produced when growing on sulfur lowers the pH of their environment to pH1.5-1.8. Different biomining bacteria are found at different temperatures. The bacteria considered to be most important are Acidithiobacillus ferrooxidans, Acidithiobacillus caldus and Leptospirillum species (all Gram negative, and within the temperature range 25-40 °C), as well as Sulfobacillus species (Gram positive, and found within the temperature range 45-60 °C).
Research on biomining bacteria concerns the mechanisms of resistance to heavy metals, with emphasis on the molecular genetics of arsenic resistance. Plasmids have been isolated and sequenced from Leptospirillum ferrooxidans, At. caldus and Sulfobacillus, and are the focus of studies on both plasmid biology and the development of genetic systems for these bacteria. Recent work has focussed on the use of a conjugational system for the transfer of plasmids from Escherichia coli to At. caldus, and the subsequent creation of “knock-out” mutants of At. caldus.
1. Biomining
