Professor Elizabeth Watkin attended the inaugural AusME (Australian Microbial Ecology) Conference in Melbourne 20 to 22 February where she gave two presentations entitled ‘Incorporation of indigenous microorganisms increases leaching rates of Rare Earth Elements from Western Australian Monazite’ and ‘Acidihalobacter prosperus, a halophilic acidophile, has unique mechanisms to survive high chloride concentrations at low pH’.
The abstracts are as follows:
Incorporation of indigenous microorganisms increases leaching rates of Rare Earth Elements from Western Australian Monazite
Melissa K Corbett1, Jacques J Eksteen2, Xi-Zhi Niu3, Elizabeth L J Watkin1
1School of Biomedical Sciences, CHIRI Biosciences, Curtin University, GPO Box U1987, Perth, WA 6845, Australia
2 Western Australian School of Mines, Curtin University, GPO Box U1987, Perth, WA 6845, Australia
3 Curtin Water Quality Research Centre, Department of Chemistry, Curtin University, GPO Box U1987, Perth, WA 6845, Australia
Rare Earth Elements (REEs) are an essential component in most modern technologies and play a key role in medical technology, environmental protection, energy efficiency, digital technology and defence. Decrease in global supply and ever increasing demand for REEs provides Australia, and in particular Western Australia, with an opportunity to become a major player in the REE industry. Conventional REE processing methods are complex, costly, use aggressive reagents and they are harsh on the environment. As an alternative to this approach this study investigated the use of phosphate solubilising microorganisms (PSMs) to liberate REEs from REE phosphate minerals. Numerous microbial species are capable of transforming insoluble forms of phosphate to soluble forms and are applied in agricultural settings (Igual et al., 2001). This study applied the use of known PSM’s to the leaching of REEs from a Western Australian monazite ore.
Monazite was added at a 0.5% pulp density to PVK media and REE levels in the leachate analysed by ICP-EOS. Of twenty five known PSB tested the best performer, a Penicillium sp. successfully released bound REEs (Ce, La, Nd and Pr) preferentially over potential ‘contaminants’, thorium and iron, from the sterile monazite into the leachate, at a total concentration of 12.32 mg L-1. These microbial isolates leached REEs from the MWM in quantities significantly greater than was recorded with abiotic dissolution of the ores alone. Indigenous microorganisms present on unsterilized monazite leached the REE’s at very low levels 0.9 mg L-1 however, inoculation of unsterilized monazite with the previously tested phosphate solubilisers, enabled us to increase the levels of REE released into the leachate four fold. A synergistic effect of between indigenous and inoculant microorganisms was demonstrated.
Acidihalobacter prosperus, a halophilic acidophile, has unique mechanisms to survive high chloride concentrations at low pH
Elizabeth LJ Watkin1, David S Holmes 2 and Mark Dopson 3
1School of Biomedical Sciences, Curtin University, Perth, Australia.
2 Center for Bioinformatics and Genome Biology, Fundacion Ciencia y Vida and Faculty of Biological Sciences, Andres Bello University, Santiago, Chile.
3 Centre for Ecology and Evolution in Microbial Model Systems (EEMiS), Linnaeus University, Kalmar, Sweden.
High concentrations of chloride ions inhibit the growth of acidophilic iron and sulfur oxidizing microorganisms used in biomining, a problem particularly relevant to Western Australian and Chilean biomining operations. This growth inhibition is due to the chloride ion disrupting homeostatic mechanisms resulting in acidification of the cytoplasm. Acidihalobacter prosperus is an acidophile that has been shown to oxidize iron at levels of NaCl as high as 50 g.L-1. However, little is known about the mechanisms this microorganism adopts in order to tolerate such high chloride ion concentrations. This study applied proteomics to elucidate how A. prosperus alters its proteome under high chloride concentrations.
A. prosperus (DSM 5130 T) was grown in the presence of sub-optimal (3.8 g.L-1) and optimal (30 g.L-1) NaCl concentrations. Total soluble proteins produced by cells were compared using 2D LC mass spectrometry with iTRAQ. Spectral data were analysed against a protein sequence database for the whole genome using ProteinPilot™ 4.5 Software.
Analysis of differential expression showed that A. prosperus adopted several changes in its proteome in response to increased NaCl levels. These included maintenance of cell wall and outer membrane function and increased abundance of proteins involved in iron and sulfur oxidation. However a reduction in proteins involved in carbon metabolism was noted. A range of osmotic responses were seen including synthesis of compatible solutes and transport proteins. The two component signal transduction osmolarity response regulator was uniquely expressed at high salt conditions. Gaining an understanding of the range of mechanisms that acidophilic iron oxidizing microorganisms may use to help the cell function in the presence of elevated concentrations of chloride can be applied to the development of saline biomining operations or improve alterative processes.
Acknowledgements: Fondecyt 1130683. This study was funded by a Bioplatforms Australia Omics grant.
Professor Elizabeth Watkin also gave a presentation to the Geomicrobiology group in the School of Earth Sciences, University of Melbourne.
The Cell Signalling symposium was held in February 2017 at Curtin University. It was organised by Professor Marco Falasca and Dr Rodrigo Carlessi presented at the conference. The symposium was a fantastic success.