The trigger mechanisms and the gene regulatory pathways of organic acid secretion during the vanadium-titanium magnetite tailing bioleaching

The long-term mining of vanadium-titanium (V-Ti) magnetite has generated a large accumulation of tailings, which can lead to metal pollution via microbial bioleaching. Current research has focused on the bioleaching of minerals, and a few studies have explored microbial responses to metals only through limited metabolite concentrations. However, the trigger mechanisms of metal release during the V-Ti magnetite tailing bioleaching and key gene regulatory pathways for organic acid metabolism are still unclear. This study screened a bioleaching fungus from the V-Ti magnetite tailing pond groundwater. The fungus promoted tailing dissolution by secreting more organic acids (808.99 mg L^-1) than without tailings (671.11 mg L^-1). The released metals were responsible for the difference in organic acid metabolism. The tailing-released Fe, Zn, and V were the triggers for the organic acid secretion via up-regulating the functional genes of citric, formic, and succinic acids in the TCA cycle, Methane metabolism, and D-arginine and D-ornithine metabolisms. Fe and V also led to the accumulation of malic acid through up-regulating functional genes during the conversion of phenylalanine, tyrosine, and glycine. Ni and Cu were the inhibitors by up-regulating related functional genes and promoting the conversion of acetyl-CoA to acetoacetyl-CoA, resulting in a decrease in organic acid concentrations. This study demonstrated the triggering metals of bioleaching and fungal gene regulation pathways, which provide a novel strategy for fungi domestication by considering the up-regulating metals to improve the bioleaching efficiency.