University of Dundee

In Tackling Lead Pollution, Fungi May Be Our Friends

06 Jan 2012

Fungi may be an unexpected ally in efforts to keep hazardous lead contamination under wraps. That’s based on the unexpected discovery by researchers at the College of Life Sciences that fungi can transform lead into its most stable mineral form.

The findings, reported in the journal Current Biology, suggest that this interaction between fungi and lead may be occurring in nature anywhere the two are found together. It also suggests that the addition or encouragement of fungi may be a useful treatment strategy for lead polluted sites.

“Lead is usually regarded as a pretty stable substance,” said Professor Geoffrey Gadd, of the Division of Molecular Microbiology at the College of Life Sciences, University of Dundee. “The idea that fungi and other microbes may attack it and change its form is quite unexpected.”

Lead is an important structural and industrial material but an unfortunate consequence of its popular use in everything from firearms to paint has been that lead contamination is a serious problem worldwide.

There have been efforts to contain lead in contaminated soils through the addition of a source of phosphorus, an element that enables the incorporation of lead into a stable pyromorphite mineral. But that change had been considered a purely chemical and physical phenomenon, not a biological one. That is, until now.

In the new study, the researchers carefully examined lead shot after it had been incubated with and without fungi. In the presence of fungi, the lead shot began to show evidence of pyromorphite formation after one month’s time.

That stable lead-containing mineral continued to increase in abundance with time. Minerals found on the surface of lead shot incubated without fungi represented less stable forms that resulted from normal corrosion.

“It seems the ability of many fungi to produce organic acids or other substances may be very important in attacking the lead and releasing forms of free lead including lead complexes, which can then react with phosphorus sources to form pyromorphite,” Professor Gadd explained.

While not all species of fungus are able to transform lead in this way, it appears many of them can, he added. It’s not entirely clear why some fungi do this, but it might assist their survival in contaminated soils.

The discovery is yet another example of the “amazing things that fungi, and microbes more generally, can do in the environment,” says Professor Gadd. “Even metals can be subject to microbial colonization and attack.”