Unique Metabolic Responses to Hypoxia and Nitric Oxide by Filamentous Fungi

Abstract

To understand fungal metabolism under stress is important for the industrial production of organic acids and enzymes from fungi, and also for traditional large-scale fermentation because inadequately controlled cultures impose stress on fungi that reduces performance efficiency. This chapter describes recent advances in studies of the hypoxic regulation of fungal metabolism. Transcriptome and proteome analyses of the model filamentous fungus Aspergillus nidulans have identified global metabolic changes in carbon source utilization and energy conservation under hypoxia. Insufficient nitrate reduction under hypoxia results in the generation of nitrite or reactive nitrogen species (RNS) that constitute a prevalent nitrogen source for filamentous fungi such as Aspergillus. Fungi have developed novel nitrate reduction mechanisms to survive under hypoxia that are likely to be industrially important because they can generate RNS during fermentation. This chapter also describes recent findings of heme biosynthesis and nitrosothionein that are involved in fungal responses to RNS and detoxification mechanisms.