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  • Writer's pictureAlex Sherman

A Concert in the woods, Heavy Metal and its Biggest Fan: Fungi

Updated: Apr 26


Have you ever eaten a mushroom because it was the healthy choice? Have you ever been to a metal concert because you’re a metal head? For most people; heavy metal is a genre of music and mushrooms are just another food to eat. But, mushrooms are not only a good topping on pizza, they are a complex organism that can cover the floor of our forests and grow near streams to sequester heavy metals and other pollutants contaminating our drinking water and polluting our farms. Human industrialization has caused harm to our environment from heavy metals and pesticides leaching into our groundwater and waterways. Using mushrooms to remediate soils reduces the contamination caused by industrialization.


Microbes have the ability to bind heavy metals in aqueous solutions in a process called biosorption (Singh, 2006). Fungi, a type of microorganism, have the ability to bind heavy metals in a process called mycosorption (Singh, 2006). Using fungi to bind to these heavy metals removes them from solution and lowers the possibility of water contamination by immobilizing the heavy metals with mycelium. Paecilomyces marquandii is an example of a fungi that has a high resistance to heavy metals; the fruiting body of which can be used to remove contaminants in soils. However, all metals become toxic at different levels, and they can become toxic to even microorganisms being used to treat the contamination (Rasool, 2014).


Understanding our effect on nature is the first step to solving the problem we created. Using natural methods for remediating the problem is the second step. Singh describes the use of fungi to remediate heavy metal contaminations in three steps: “(1) biosorption of metal ions on the surface of fungi, (2) intracellular uptake of metal ions, and (3) chemical transformation of metal ions by fungi (Singh, 2006).” So, some fungi can use their mycelia to sorb metal ions but sometimes their concentration in the soil is too high, reductase and peroxidase enzymes can help break down metals and allow for uptake into fungal bodies. Removal of the fruiting body or mycelia is removal of the metal from the environment.


We don’t eat most fungi that grow out in nature, the ones we most commonly enjoy are commercially produced inside warehouses and they are grown as a commodity. However, this also means we aren’t getting the same micronutrients that wild fungi contain. Oyster mushrooms are very common to find at a farmers market but they have so many other uses. Pleurotus spp. is white-rot fungi that helps break down lignin (very hard to decompose or break down) but it also creates sorption of heavy metals to the growing body of its mycelium (Ruiz, 1999). This is why we can get so many vitamins and minerals from a small serving of mushrooms. Oyster mushrooms, Pleurotus spp., are saprophytic fungi—they break down plants and animals (i.e. decomposers) but they have a higher rate of fruiting and have a smaller mycelial network compared to body weight produced.


Mycologists have theorized how oyster mushrooms are advantageous to other mushrooms because they are nonspecific and non-selective in what they choose to decompose. Should we eat the mushrooms grown near heavy metal contaminated waste sites? No. Similar to our agricultural fields, we shouldn’t consume foods that are grown in polluted soils. But most plants don’t sequester heavy metals as well as fungi do. This is why using mushrooms as a form of bioremediation can help not only contaminated groundwater but farmland as well.


Removing heavy metals from soil is hard and the result in a lot of by products. Fungi make the process easy but it still leaves a lot of waste. “Dead fungal biomass can be immobilized in polyacrylamide, alginate, polysulfone, textile fibers, and inorganic compounds for the removal of metals (Singh, 2006).” This makes them ideal for removing heavy metals they sequester and remove them without the chance of reintroducing the metals into the ecosystem. Using the dead fungal biomass as alternatives in vehicles and other industrial parts can make the whole process sustainable.


Heavy metals can change form in soils from interacting with different enzymes exuded from microorganisms. Peroxidases and reductases change the ionic charge on the metals which in turn changes how they interact with other chemicals in solution. The solution in this case is soil. Fungi can excrete different enzymes that reduce the metals modifying the metals to be less mobile and toxic (Singh, 2006). The main mechanisms that fungi transform metals include methylation, reduction and dealkylation of the metals. So far, as humans, we cannot accomplish these feats that fungi have been able to do so seamlessly for the past thousands of years, but we can incorporate fungi into the systems we believe need fixing. “The diverse oxidative and reductive methods of degradation or biotransformation of recalcitrant compounds make its application magnetic in various matrices. (Purohit, et. al., 2018) We can apply mushrooms to many substrates and receive almost the same effect across the board: they decompose complex hydrocarbons into H2O and CO2.


Utilization of fungi as a form of bioremediation has been less than prolific in the past. It is our duty as humans that when we make a mess, we will clean it up. Incorporating fungi into bioremediation systems can help keep ourselves healthy but also keep our ecosystems healthy. Healthy soils means safe drinking water and safe foods being grown. To strive for a better future we must correct the mistakes we have made and solve the problems at hand…with fungi.


 

Citations


Purohit, J., Chattopadhyay, A., Biswas, M., & Singh, N. (2018). MYCOREMEDIATION AND ENVIRONMENTAL SUSTAINABILITY: Volume 2. Place of publication not identified: SPRINGER INTERNATIONAL PU. doi:https://doi.org/10.1007/978-3-319-77386-5_4


Rasool, A., & Irum, S. (2014). Toxic Metal Effect on Filamentous Fungi Isolated from the Contaminated Soil of Multan and Gujranwala, Journal of Bioresource Management, 1.


Ruiz-Duenas, F. J., F. Guille´n, S. Camarero, M. Pe´rez-Boada, M. J. Martınez, and A. T. Martı´nez. 1999. Regulation of peroxidase transcript levels in liquid cultures of the ligninolytic fungus Pleurotus eryngii. Appl. Environ.Microbiol. 65:4458–4463.


Singh, Harbhajan. Mycoremediation: Fungal Bioremediation. John Wiley & Sons, 2006



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