Identification and characterisation of bacteria isolated from a platinum mine

Sodi, Koketso
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Bioleaching involves the solubilisation of metals from solid insoluble substrates such as minerals using microorganisms. Bacteria isolated from mines could have properties that are desirable in the metal bioleaching field. These include iron and sulphur-oxidation and organic acid production. The aim of this study was to isolate, identify and characterise bacteria from a platinum mine. Bacteria were isolated from the concentrator plant of a platinum mine and enumerated using traditional microbiological techniques. The bacteria were then identified using Sanger sequencing and NCBI-BLAST. The colony morphology of the bacteria was noted, and the cellular morphology of the bacteria was analysed using gram staining. To find the optimum growth media for the bacteria, growth curves were conducted in Luria-Bertani, nutrient and 9K broth. Organic acid production by the bacteria was analysed using high-performance liquid chromatography. The results showed that the isolated indigenous bacteria grew well in soils with a pH between 6-9. The colony-forming units of bacteria from each sampling site showed that there was a substantial abundance of bacteria in and around the concentrator plant. A total of 50 bacterial isolates were identified and Proteobacteria was the dominant bacterial phylum. Six bacterial isolates namely Bacillus sp., Pseudoxanthomonas mexicana, Pseudomonas stutzeri, Arthrobacter globiformis, Pseudomonas aeruginosa and Pseudomonas brassicacearum had desirable bioleaching characteristics and were selected for further characterisation. The bacteria were able to produce gluconic, citric, lactic, propionic, butyric, formic, and indole-3-acetic acid. Therefore, they can potentially be used for the bioleaching of platinum group metals.
A dissertation submitted in fulfilment of the requirements for the degree of Master of Science in Molecular and Cell Biology to the Faculty of Science, School of Molecular and Cell Biology, University of the Witwatersrand, Johannesburg, 2022