At the present time, the average grade of gold in deposits being mined is decreasing, and the prevalence of feed components that negatively impact the cyanidation process, is increasing. Thiosulfate is an alternative lixiviant that is often suggested as a cyanide replacement. There are many challenges associated with the implementation of thiosulfate gold leaching, most prevalently the high consumption of reagents during leaching, increasing the cost. The literature of the past two decades has focused on the use of additives and solution conditions to slow decomposition of the reagent. Alternatively, biogenic production of thiosulfate is another path towards the development of feasible thiosulfate gold extraction methods. In this study, the design of a biogenic thiosulfate leaching method has been developed for the first time. First, a comprehensive study of the literature from many disciplines was conducted to identify potential microorganisms. The bacterium Methylophaga sulfidovorans was selected for laboratory study. Different substrates were used to produce biogenic thiosulfate and evaluated based on yield and conversion efficiency. Sodium sulfide was determined to be the most effective with biogenic thiosulfate (Bio-TS) production reaching a maximum of 1.9 g/L in testing. Next, the viability of Bio-TS gold leaching was tested using leaching experiments on oxide ore where maximum gold extraction of 62 % after 24 h at 10% pulp density in a stirred tank system was obtained. In the final research chapter, the effect of solution conditions and additives were explored with respect to gold extraction efficiency, Bio-TS consumption, and effects on other solution components during leaching. Gold leaching efficiency was increased by 66 % and copper precipitation decreased by 40 % with the addition of 10 mmol/L ethylenediaminetetraacetic acid (EDTA) and 0.1 mol/L ammonia due to coordination reactions with copper ions in solution. The kinetics of the system were modelled using the shrinking core model and determined to be limited by diffusion to the gold surfaces in the ore particles (R2 > 0.994). Additionally, the thermodynamics of the system were modelled to determine the reduced stability zone of the aqueous copper complexes. Finally, the potential and limitations of this method were summarized.