Phosphorus Uptake, Storage and Utilization by Fungi

This chapter presents the phosphorus uptake, storage, and utilization by fungi. Fungi are a diverse group of lower plants united by their heterotrophic mode of nutrition. Studies of fungal nutrition have, thus, not unnaturally been dominated by considerations of carbon metabolism. The chapter draws together some of the scattered data available on fungal Physiology and uptake. It includes the various yeasts that are sometimes segregated from the filamentous fungi. The approach is basically biochemical and orientated towards laboratory studies. Many of the studies discussed in the chapter have attempted to define the fundamental cellular processes of phosphorus (P) metabolism and have concentrated on only a few fungal species; notably on a handful of fast-growing, easily cultured yeasts (species of Saccharomyces and Candida), and the filamentous species—Aspergillus niger and Neurospora crassa. The development of X-ray microanalysis techniques for use with the electron microscope has provided a powerful tool for investigating ion distribution at the cellular level. The P content of the cell wall is highly variable, depending on the species, the structure that the wall came from, and on the growth conditions. It is striking that the cell walls of the zygomycetes, Cunninghamella and Mucor have very high P levels in comparison with those of other fungi. Extensive depletion of most P compounds of the cell is incompatible with continued growth. However, under conditions of restricted P supply, the effects have been found is a reduction in the total P content of sulfur (S). An understanding of the role of polyp in the P economy of the cell requires both the knowledge of the enzymes involved in its metabolism and its rates of turnover in the cell. The enzymes of polyp metabolism are discussed in the chapter.