central nervous system known as domoic acid (Figure 8.7). This com-
pound had been produced byNitzschia pungens, a chain-forming diatom
of the phytoplankton which is now referred to the genusPseudonitzschia.
8.4 Toxigenic Fungi
The fungi are heterotrophic and feed by absorption of soluble nutrients
and although many fungi can metabolize complex insoluble materials,
such as lignocellulose, these materials have to be degraded by the
secretion of appropriate enzymes outside the wall. A number of fungi
are parasitic on both animals, plants and other fungi, and some of these
Figure 8.6 Cyanoginosin
Figure 8.7 Domoic acid
280 Non-bacterial Agents of Foodborne Illness