Lead Bioprecipitation by Yeasts Utilizing Organic Phosphorus Substrates

Abstract

ABSTRACTYeasts can exhibit various mechanisms that effect changes in metal speciation, toxicity and mobility. This research has examined the role of yeast phosphatases in lead bioprecipitation when utilizing an organic phosphorus-containing substrate as the sole phosphorus source. The formation of lead-containing biominerals after growth with organic phosphorus sources (glycerol 2-phosphate, phytic acid) was demonstrated and it was found that test yeasts were capable of mediating precipitation of lead phosphate (Pb3(PO4)2), pyromorphite (Pb5(PO4)3Cl), anglesite (PbSO4), and the lead oxides massicot and litharge (PbO), with variations in the mineral types produced between the different species. All test yeasts produced pyromorphite, and most produced anglesite. Lead oxides were only detected with Pichia acacia. Lead-containing precipitates were also formed if yeast cells were pre-grown in organic-phosphorus-containing media and subsequently exposed to Pb(NO3)2. The role of phosphatases in mediating the formation of lead-containing minerals has provided further understanding of potential fungal roles in metal and mineral biogeochemistry as well as the possible significance of these mechanisms for element biorecovery or bioremediation.