Utilisation of nitrogen compounds

Fungi can utilise nitrate, nitrite, ammonia (see footnote, p. 82) and a very wide range of organic nitrogen compounds. Some idea of the diversity of the latter can be gained by reference to an older text such as that by Cochrane (1963), in which the capability of fungi to use a wide diversity of compounds is less taken for granted than is often the case now. The same volume and those of Hawker (1950) and of Lilly & Barnett (1951) give useful information about fungi which are able to utilise:

1. Nitrate nitrogen.

2. Ammonia or organic nitrogen but not nitrate nitrogen.

3. Only organic nitrogen.

At the time the above authors were writing, there was debate about whether or not fungi are able to use atmospheric nitrogen. That debate was prior to the use of 15N for detecting nitrogen fixation. Since the isotope became available, it has been established now that no known fungus is able to fix atmospheric nitrogen (Stewart, 1966). Of course, fungi lichenised with cyanobacteria form organisms that are able to use this source of nitrogen.

The ability to use nitrate nitrogen represents a greater capability on the part of a fungus, for all nitrate users can use ammonia but not all ammonia users can use nitrate. A list of some fungi known to be able to use nitrate is given in Table 6.1. It gives an indication only; to obtain anything like completeness would be impossible.