Fungal adaptation in extreme temperatures

Jeenisha Dabreo Rumao

Researchers from SASTRA University have uncovered how some fungi can withstand high temperatures. The study published in Proteins discovered that certain proteins on the outside of fungi play a crucial role in making them heat-resistant. Understanding heat-resistant proteins can help us build proteins and enzymes for industrial use where temperatures are usually high.

Jeenisha title image
Properties of proteins in thermophilic fungi that enable them to survive high temperatures, identified through structure-based and sequence analysis. Credits: Shricharan.

Fungi such as mushrooms, yeast and mould are most commonly found in moderate room-temperatures. However, some fungi can thrive in high-temperatures, and were discovered nearly a century ago. This study has paved the way to understand the molecular intricacies that enable fungi to withstand extreme temperatures. 

Fungi are known to play a crucial role in the ecosystem and typically thrive in mesophilic environments characterized by moderate temperatures. However, certain species exhibit thermophilic properties, enabling them to survive in elevated temperature conditions, such as compost heaps and geothermal areas. Ragothaman Yennamalli, Assistant Professor at SASTRA University, Thanjavur, expressed, We wanted to understand their unique adaptation mechanisms for potential industrial use.’

His group delved into fungal proteins to elucidate molecular features contributing to their heat resistance. First, they identified 14 thermophilic fungi and their close mesophilic counterparts, creating a dataset including their proteins. To understand the evolutionary history and biological role of the identified proteins, researchers utilised eggNOG’, a bioinformatics tool to group proteins or genes into clusters of orthologous groups (COGs). As orthologous group genes and proteins stem from a common evolutionary ancestor, this categorisation provided insights into the functional conservation and relation of genes across different species. 

This study significantly found that features contributing to the stability and functionality of proteins in extreme heat, such as charge and exposed polar residues, are more prevalent in thermophiles than in mesophiles. Yennamalli added, After identifying the specific features enriched in thermophiles, we reached a point where we couldn’t discern a clear pattern in the entire proteome study. Thus, seeking a fresh perspective, we focused on the proteins secreted outside the fungal body for metabolic processes — the Carbohydrate-Active Enzymes (CAZymes).’

The carbohydrate-binding modules (CBMs) of the CAZymes break down carbohydrates. They compared the relationship between thermophilic and mesophilic proteins within the CAZymes family and identified pairs of proteins that shared about 60% of their genetic makeup. Next, they investigated the CBMs of the identified CBMs and observed that proteins resistant to high temperatures are more water-repellent and contain aromatic molecules and positive charge. These interactions contribute to the stability and structure of the protein. Yennamalli is confident,

Understanding these interactions is highly important as it will help in designing more stable proteins, which can have practical applications in industries where enzymes are required to function under extreme conditions.

As the study progressed, it drew parallels with bacterial proteins and recognised shared factors such as salt-bridges and charged residues that contribute to protein stability in thermophilic fungi. However, while proposing that the hydrophobic interactions, disulphide bonds, and electrostatic interactions may be responsible for the thermophilic property of fungi, the researchers stressed on the importance of more experiments to confirm these findings. 

Jogi Madhuprakash, Assistant Professor at University of Hyderabad, pointed out that the study provides detailed methods on protein analysis and structural comparisons, and acknowledges the need for experimental validation. He also pointed out that there are other alternative explanations like environmental variations or unrelated evolutionary adaptations, which could help in understanding thermostability in fungi. He suggested that conducting experiments on surface-exposed and charged residues across a broader range of fungi could strengthen the findings. Shricharan Senthilkumar, lead author and third-year bioinformatics student at SASTRA University is hopeful, 

The insights gained from this study on fungal thermostability lay the groundwork for developing more resilient enzymes for biofuel production.

The findings of the study can enable the use of fungi to improve agricultural productivity, optimise industrial processes, and drive advancements in biotechnology.

Written By

Jeenisha is biotechnology postgraduate pursuing her passion for science as a microbiologist. She believes that writing will help her develop a better insight into the field and aid in bridging the gap between research and communication.