Specialized Fungi Can Reduce Heavy Metal Contaminants and Improve Soil Health

As rapid industrialization continues to take hold of our planet, our soil and water have become increasingly contaminated with toxic heavy metals like cadmium, lead, and arsenic. This form of pollution is incredibly harmful to human health and global ecosystems, yet there are minimal solutions to effectively contain or reverse the dangerous levels of these heavy metals in our environment. In a move to reduce these contaminants, researchers from Nnamdi Azikiwe University, Nigeria, have uncovered the mechanisms behind certain fungi that are capable of cleaning up heavy metals from the soil, offering more insights into this natural soil remediation technique.

Combatting contaminants with fungi

Phosphate-solubilizing fungi (PSF) are specialized microorganisms that can break down inorganic phosphorus compounds to release phosphorus into a form that plants can use. This process is not only beneficial for the growth of plants but also plays a significant role in immobilizing heavy metals and making them less harmful to the environment. When the fungi transform phosphorus into a bioavailable form, they inadvertently bind heavy metals into the soil. As a result, the metals are stopped from being absorbed by plants, which reduces their entry into the food chain and ecosystem. PSF locks these heavy metals away through multiple mechanisms. 

One primary method is through biosorption, when the cell structures of the fungi act like sponges, absorbing and binding the heavy metals directly into their cells (1). Fungi also produce organic acids that can bind to heavy metals and transform them into stable, nontoxic forms that plants or other living organisms cannot easily absorb. This enhanced adsorption capacity means that more metals can be held tightly by the soil particles. Additionally, PSF activity in the soil can lead to changes in the soil’s pH, making the environment less conducive to the mobility and solubility of heavy metals. 

Researchers have found that when PSF is combined with phosphate minerals, they work even better at releasing phosphorus for plant use while also locking away heavy metals so that plants cannot take them up. Once this method is fully understood, it may provide a new way to depollute the soil and contribute to its overall health (2).

Bioremediation for cleaner soil

Mycoremediation is a form of bioremediation that uses fungi to clean up waste. The unique qualities of many different kinds of fungi have shown potential in reducing a variety of environmental contaminants. This eco-friendly process allows for a more sustainable and affordable means of effectively cleaning up heavy metal contamination.

Because pH can affect the solubility of heavy metals and metalloids in the soil, researchers believe that future studies should focus on determining the efficiency of the PSF and phosphate material combination to remediate polluted soils. The future of this research should also examine the effect of PSF and beneficial bacteria interact and how these interactions can help immobilize heavy metal pollution in the soil. Nonetheless, if PSF can be harnessed more effectively, it could lead to the development of a natural and cost-effective strategy for cleaning up contaminated soil across the globe.

References

1. Ramya, D., N. Jennifer Michellin Kiruba, and A. Joseph Thatheyus. 2021. “Chapter 15 - Biosorption of Heavy Metals Using Fungal Biosorbents – a Review.” Edited by Vijay Kumar Sharma, Maulin P. Shah, Shobhika Parmar, and Ajay Kumar. ScienceDirect. Academic Press. January 1, 2021. https://www.sciencedirect.com/science/article/abs/pii/B9780128219256000150?via%3Dihub.
2. Christopher Uche Okolie, Ann Onyinye Mbaukwu, Chidozie Azubuike Anukwuorji, and Chukwu Nkumah Okereke. 2024. “Immobilization of Heavy Metals in Contaminated Soils Using Phosphate-Solubilizing Fungi: Mechanisms and Advantages.” Natural Resources and Conservation 10 (1): 1–6. https://doi.org/10.13189/nrc.2024.100101.