Biomining is a growing industry aimed at providing an economically feasible alternative, to extract valuable metals from low grade ores as compared to conventional extraction techniques. Acidophilic iron and sulfur oxidising microorganisms are currently used in this process however, these microbes are sensitive to chloride ions. Fresh water is therefore required for biomining processes which challenges the economic feasibility in countries where fresh water is scarce. Thus, this study aims to explore acid saline lakes, in search for iron and sulfur oxidising acidophiles that are chloride resistant. Lake Tyrrell, an acid saline lake in north western Victoria, harbours the niche environment in which these microbes would most likely be present, as it has low pH (~4), high salinity (>200 g.L-1 NaCl) and large iron and sulfur deposits. Water, sediment and biofilm samples were collected, and the diversity of the microbial populations determined using culture and non-culture dependant methods. Enrichment cultures were grown in Basal Salts media at both 35g/L and 105g/L NaCl at the pH of the sampling site (ranging from pH 4-5). Chloride tolerant acidophilic iron and sulfur oxidising microbes were isolated from ferrous iron overlay plates (Johnson & Hallberg 2007) inoculated with the enrichment cultures. From all samples, microbial growth was observed at both NaCl concentrations however, iron oxidation was only observed in enrichment cultures from biofilm samples at both NaCl levels. 16S rRNA gene amplicon analysis revealed the lake samples to be very diverse. The most abundant taxa present in the sediment and biofilm samples from the lake were from the families Halobacteroidaceae, Balneolaceae, Deferribacteraceae and Salinisphaeraceae.
This study has resulted in the isolation of an acidophilic iron oxidising microbes that may have an application in the biomining industry as well as giving an indication of the microbial diversity of Lake Tyrrell.