ABSTRACT
The discovery of penicillin, a secondary metabolite of Penicillium notatum West ( = P. chrysogenum Thorn), in 1929 marked a milestone in the development of antibiotics. In the intensive studies that followed this discovery, mycologists and microbiologists searched for further sources of antibiotics by investigating microbial antagonism and antibiosis. In one of the earliest studies, Weindling (1932) observed that a strain of what he believed to be Trichoderma lignorum was antagonistic to other fungi. The antibiotic agent was exuded into the cultivation medium (Weindling, 1934) and could be isolated as a crystalline compound (Weindling and Emerson, 1936). The same compound, which exhibited high fungicidal activity, was isolated from Gliocladium .fimbriatum Gilman and Abbott ( = M yrothecium verrucaria (Albert and Schw.) Ditmar ex Fr.) (Weindling, 1937) and the structure of this novel compound, named gliotoxin, was established almost 30 years later (Beecham et al., 1966). Since these pioneering efforts, interest in the secondary metabolites produced by Trichoderma and Gliocladium species has been sustained and the isolation and characterization of a considerable number of metabolites has been achieved. Interestingly, gliotoxin and related compounds have recently attracted much interest in the medical field as potential immunomodulating agents that have the ability to suppress the immune system by triggering cell suicide (apoptosis) (Jiang et al., 1993). An increasing number of metabolites from Trichoderma and Gliocladium species are being discovered by the application of bioassay-guided separation. With this technique, a biochemical assay is used to identify metabolites in an extract exhibiting a particular biochemical activity. In this way, biological activities other than antibiotic properties have been recognized for many compounds produced by Trichoderma and Gliocladium species.
