Lesley Mutch

The characterization of salt tolerance in biomining microorganisms and the search for novel salt tolerant strains

In this study an acidic saline drain in the Western Australian wheat belt was sampled and enriched for salt tolerant chemolithotrophic microorganisms in acidic media containing up to 100 gL-1 NaCl. A mixed consortium was obtained which grows at pH 1.8 and oxidises iron (II) in the presence of up to 30 gL-1 NaCl. In comparative tests (growth rates and iron (II) oxidation rates) it was found that NaCl concentrations >3.5 gL-1 generally cause reduced growth and iron (II) oxidation rates in known biomining organisms. The results help to set a benchmark for NaCl tolerance in known biomining microorganisms and will lead to the generation of a consortium of microorganisms that can oxidise iron (II) effectively in saline process water.

Population dynamics of a low-grade chalcopyrite bioleaching column

Terminal Restriction Fragment Length Polymorphism (T-RFLP) was used to determine the diversity of the bacterial and archaeal populations in a bioleaching column charged with a low-grade chalcopyrite ore and operated at 50 oC. Differing populations were identified in the leachate and the column solids but there was not discernible effect in respect of location in the column.

Analysis of the Microbial Community in the Leachate Collected from an Experimental Bioleaching Column by Cloning and RFLP

A culture independent molecular methodology was used to investigate the bacterial and archaeal microbial dynamics of leachate collected from a 60°C chalcopyrite bioleaching column inoculated with a known microbial consortium. A 16S rRNA gene clone library was constructed for both the bacterial and archaeal populations in the leachate from the column. PCR-RFLP analysis of these clone libraries indicate species dominance and generally low species diversity.

Nucleic acid extraction from biomining microorganisms

Various methods of nucleic acid (NA) extraction were investigated with the aim of developing a quantitative method of NA extraction from five representative strains of biomining microorganisms. The process of removing cells from mineral surfaces, lysing microorganisms, precipitating NA and purifying RNA were analysed. The success of each method was examined spectrophotometrically, by agarose gel electrophoresis and PCR or quantitative real time PCR (qPCR). The most important step was shown to be cellular lysis, which principally impacted on the quantity of NA extracted from each strain. The quantity and quality of extracted NA was highly dependent on the method of NA precipitation. This study resulted in the development of a NA extraction method that reliably and reproducibly extracted NA from five strains of biomining microorganisms.