Anthropogenic sources of lead contamination in soils include mining and smelting activities, effluents and wastes, agricultural
pesticides, domestic garbage dumps, and shooting ranges. While Pb is typically considered relatively insoluble in the soil environment,
some fungi may potentially contribute to mobilization of heavy metal cations by means of secretion of low-molecularweight
organic acids (LMWOAs). We sought to better understand the potential for metal mobilization within an indigenous
fungal community at an abandoned shooting range in Oak Ridge, TN, where soil Pb contamination levels ranged from 24 to
>2,700 mg Pb kg dry soil1
. We utilized culture-based assays to determine organic acid secretion and Pb-carbonate dissolution
of a diverse collection of soil fungal isolates derived from the site and verified isolate distribution patterns within the community
by 28S rRNA gene analysis of whole soils. The fungal isolates examined included both ascomycetes and basidiomycetes that excreted
high levels (up to 27 mM) of a mixture of LMWOAs, including oxalic and citric acids, and several isolates demonstrated a
marked ability to dissolve Pb-carbonate at high concentrations up to 10.5 g liter1 (18.5 mM) in laboratory assays. Fungi within
the indigenous community of these highly Pb-contaminated soils are capable of LMWOA secretion at levels greater than those of
well-studied model organisms, such as Aspergillus niger. Additionally, these organisms were found in high relative abundance
(>1%) in some of the most heavily contaminated soils. Our data highlight the need to understand more about autochthonous
fungal communities at Pb-contaminated sites and how they may impact Pb biogeochemistry, solubility, and bioavailability, thus
consequently potentially impacting human and ecosystem health.