There's Mycelium in Them Mines. Or, There Should Be.

Fungi are regularly used in agriculture as methods of fighting crop pathogens, as well as helping improve soil conditions. They are also an increasingly important tool for bioremediation, which is basically removing pollutants from the ground by planting things to act as chemical sinks. Well, it appears that certain fungi can also help clean polluted waters.
A study published in Proceedings of the National Academy of Sciences (PNAS) has found that Stilbella aciculosa produces superoxides during asexual reproduction.

Mn(II) oxidation by an ascomycete fungus is linked to superoxide production during asexual reproduction (abstract)

What is a superoxide, you ask? Chemically it is any compound that contains the superoxide anion (O₂⁻) and biologically it a toxin that is sometimes produced as an immune response to kill pathogens. However, in S. aciculosa, superoxide appears to serve as a cellular signal to help moderate cell differentiation. Fortunately for us humans it has the coincidental side effect of rapidly and efficiently oxidizing environmental manganese.

S. aciculosa with a close up of manganese oxides at the base of conidia.

As it turns out manganese oxides act as environmental sponges that can degrade carbon substrates, control the availability of nutrients and help clean up pollutants, like cadmium, and arsenic. This feature is especially useful in cleaning up these chemicals in the runoff from coal mines.
Now, S. aciculosa isn't the only organism that makes superoxides, and this isn't the first time that these chemicals have been employed to clean coal mine runoff.

The same method that causes manganese oxidation in S. aciculosa also exists and functions very similarly in the common marine bacterium genus Roseobacter. This study shows an interesting evolutionary homology between a prokaryotic and a eukaryotic organism mechanics, both even using the same enzymes.

Remediation of coal mine drainage has long been done by throwing a bunch of bacteria and fungi laced organics, like crop wastes, into the mine and hoping they will do their thing. The obvious problem here is that if you don't know how the microbe produces the reactive molecule (or why it does) than you can't develop a method to coerce it into producing it. And that means just dumping them in the mine and waiting is often ineffective.

This study, demonstrating superoxide production during asexual reproduction, presents us with new potential direction for a wide range of studies from environmental chemistry, to evolutionary biology.



Study credit: Colleen M. Hansel, Carolyn A. Zeiner, Cara M. Santelli, and Samuel M. Webb.
Photo by Colleen M. Hansel