Chapter 5 - Thermophilic fungi: Diversity, physiology, genetics, and applications

Abstract

Thermophilic fungi, unlike prokaryotes, are able to grow at temperatures not exceeding 62°C. Their moderate degree of thermophily is probably the reason behind their habitats that are not as exotic as that of thermophilic prokaryotes and also for their not being much explored until now. Their temperature limitation reflects their inability to form thermostable and functional cellular organellar membranes and proteins at elevated temperatures. These organisms thrive in humid, warm, and aerobic habitats such as compost, agricultural residues, stored grains, soil, manure, industrial coal mines, nuclear reactor effluents, etc. The metagenomic tools can aid in unraveling their diversity in different habitats and in understanding their role in their niche. They exhibit a range of physiological adaptations such as a slower metabolism, high proportion of saturated fatty acids in phospholipids, high turnover of enzymes, synthesis of heat shock proteins, difference in lipid storage mechanisms, etc., to survive. Their genome analysis reveals reduced genomic size, high G:C content, shorter introns, fewer transposable elements, and repetitive sequences. They secrete a wide array of enzymes such as amylases, proteases, lipases, phosphatases, xylanases, pectinases, laccases, cellulases, hemicellulases, and glycoside hydrolases, which have more catalytic efficiency than their mesophilic counterparts. They are used in a variety of biotechnological applications such as composting, biofuel production, bioremediation, paper production, and therapeutic biomolecule production. Their immense biotechnological potential is yet to be fully explored. Genetic engineering approaches should be relied upon to make them more efficient players for biotechnology and environmental management. This chapter is focused upon their diversity as well as the physiological and genetic adaptations highlighting their potential applications.