The first discovery: fungi can convert lead metal to phosphorus chlorite mine

A fungal species can convert lead metals to pyromorphite, according to a research paper published online January 12, 2012 in the Cell journal Current Biology. These findings highlight that microbes play an important role in geological processes, suggesting a possible bioremediation of lead-contaminated soils. This is also the first example of a fungus that plays a lead role in mineralization.

Lead metal is known to be highly toxic. Because lead is involved in early neurodevelopmental problems in children, the metal has been removed from products such as household paints, but other sources of lead pollution, such as mining operations and bullets that can be used in shooting fields, are still present. Once inside the soil, lead metal can penetrate into the water, into the food chain.

Lead metals are exposed to atmospheric, humidity and pH to produce lead oxides and lead salts. The strategy for remediation of lead contaminated soils is focused on converting lead into the most stable form of chlorophyll. It is known that fungi can detoxify other toxic compounds, such as uranium, by converting them to mineral form. So Geoff Gadd from the University of Dundee in England infer that fungi may also do the same for lead.

 Gadd's team collected samples of several fungal species in an abandoned lead mining facility in Scotland. They placed the lead warheads (in ammunition for shotguns) in agar medium in a Petri dish, and then added the fungi to some petri dishes to allow them to grow for several months.

By analyzing the elemental composition and mineral structure of compounds deposited on lead, the researchers found that lead metal incubated with a fungal species produced a higher level of phosphorus compared to placing the lead metal in a sterilized petri dish Chlorite, which means that this fungus does play a role in detoxification of lead metal.

Given the current inability to remove all of the lead metal from contaminated soils, Gadd argues that the ability of the fungus to dissolve metal elements may be used as a repair strategy.

Mineralization of lead metal minerals may be a future bioremediation strategy, but the primary task is to repeat these findings out the laboratory. Bioremediation is a black box testing method. Only by obtaining critical evidence such as how fungi are involved can help scientists design long-term remediation strategies to repair contaminated land. (Young Joon Rhee, Stephen Hillier, Geoffrey Michael Gadd, Lead Transformation to Pyromorphite by Fungi, Current Biology,2012)