Introduction

The relationship between fungi and sulphur is intriguing. Though inorganic sulphur at the most oxidised state – sulphate – is the customary source of the element when fungi are grown in culture, it is well known that sulphur-containing amino acids can be used with almost equal facility. In Neurospora crassa, for instance, when inorganic sulphur is lacking, the methionine transport is derepressed (see Chapter 6). Fungi are capable of oxidising inorganic sulphur compounds that may be important in ways other than the provision of sulphate for assimilation. Also fungi can produce volatile sulphur compounds that may be important in the natural environment. Equally, the ability of species to tolerate sulphur dioxide may be important in environments subject to air pollution. Of course the same gas is used also to preserve beverages and food, so that there is an industrial dimension to fungal tolerance of sulphur dioxide. All of the above are considered in more detail in the sections that follow.

The emphasis of this chapter is on inorganic sulphur as the source of the element for a fungus. The evidence from culture studies is compatible with an almost universal ability to utilise inorganic sulphur. As far as I am aware, inorganic sulphur compounds cannot be released from organic sulphur compounds in the external medium of a fungus. Nevertheless fungi contain sulphatases that release sulphate from organic form. An interesting example of this is the utilisation of glucose 6-sulphate by N. crassa (Reinert & Marzluf, 1974).