Response Mechanisms to Chemical and Physical Stresses in Yeast and Filamentous Fungi

Abstract

Free-living unicellular eukaryotes, including yeast and filamentous fungi, remain in close contact with the surrounding environment throughout their existence. Such a lifestyle facilitates the absorption of life-supporting nutrients but inevitably exposes these organisms to the hostility of the elements. Consequently, they experience various chemical and physical stresses, often collectively dubbed as abiotic stress, and mounting appropriate protective measures against the aggressive exterior is the essence of their survival. In this chapter, the stresses of extreme pH, low temperature, extreme hydrostatic pressure, hyperosmosis, and dehydration will be discussed. The modes of toxicity of these stresses will be described, as well as the methods used by cells to tolerate them. In accordance with the central theme of this book, the machineries of sensing and responses to those stresses will be emphasized. On the surface they seem diverse; however, at the basal level, the damage to cellular functions is often similar, as reflected by the resemblance of the cellular regulatory responses. Moreover, cellular protection mechanisms against various physical and chemical stresses are also strikingly convergent. These similarities will be highlighted in this chapter. The importance of studying fungal response mechanisms to chemical and physical stresses for industry and medicine will also be succinctly delineated.