Ovine ill-thrift in Nova Scotia. 9. Production of experimental quantities of isocyanide metabolites of Trichoderma hamatum

Abstract

Laboratory cultures of Trichoderma hamatum produce metabolites that are characterized by an isocyanide functionality. Three such metabolites predominate. One is the known compound trichoviridin (I). The other two, described here for the first time, are 3-(3-isocyano-6-oxabicyclo[3,1,0]hex-2-en-5-yl)acrylic acid (II) and a very unstable compound 3-(3-isocyanocyclopent-2-enylidene-)propionic acid (III). Production of these three metabolites by a random sample of wild isolates of the fungus has been examined. At least one of these isocyanides was isolated from all cultures in which the culture broth inhibited the growth of Micrococcus luteus. The relative amounts of the three isocyanides produced by individual isolates were not the same and cultures were found in which I, II, or III was the main product. The isocyanide III was produced by all wild isolates which had antibiotic activity in their culture broth, and it was present in the concentration range 2-40 mg X L-1.

Secondary metabolites from species of the biocontrol agent Trichoderma

“…Cyclopentylisocyanide metabolites have been found to have physiological activity in three distinct fields: (I) induction of bacteriostasis in vivo and in vitro of functionally important rumen bacteria and the reversal of this activity by nickelous ion (Brewer et al 1982(Brewer et al , 1986(Brewer et al , 1990; (II) induction of oospores of the A2 mating type of Phytophthora spp. and other effects on fungal morphology (Pratt et al 1972;Reeves and Jackson 1972;Brasier 1975); (III) inhibition of the enzyme tyrosinase and its implication for melanin biosynthesis in mammals (Lee et al 1997a, b).…”

Fungal Antibiosis in Biocontrol of Plant Disease

“…In a singular case, an indirect deleterious effect on ruminants caused by antibioticproducing fungi has been reported. The antibiotic chaetomin from Chaetomium globosum (13,50) and certain isocyanide metabolites from Trichoderma hamatum (52) were shown to be toxic to symbiotic bacteria that digest cellulose in ruminants. Thus, these soil-inhabiting fungi have been implicated in ovine ill-thrift disease (13,50,52).…”

“…The antibiotic chaetomin from Chaetomium globosum (13,50) and certain isocyanide metabolites from Trichoderma hamatum (52) were shown to be toxic to symbiotic bacteria that digest cellulose in ruminants. Thus, these soil-inhabiting fungi have been implicated in ovine ill-thrift disease (13,50,52). This example shows that potential nontarget effects of compounds produced by biocontrol agents must be carefully evaluated before such organisms or substances are applied on large scale in agricultural practice.…”

The antibacterial activity of alamethicins and zervamicins

“…Micrococcus luteus Schroeter (HLX 701, held at the Atlantic Research Laboratory) was maintained and cultivated as described by Brewer et al (1970). The cellulolytic culture of rumen micro-organisms used in this work has been described (Brewer et al 1982). It was maintained by weekly transfer on rumen diluent (Kurihara et al 1968) using rumen fluid that had not been centrifuged, without added soluble sugars, but with a paper strip (Whatman No.…”

“…The test solutions were then allowed to diffuse at 35°C for 24 h, when the plates were overlaid with a suspension (ca lo5 ceIls/ml) of Mic. luteus in nutrient agar at 45°C (Brewer et al 1982) such that the overlay covered the agar but did not submerge the paper discs. The cultures were incubated at 35°C for 24 h and the clear zones of inhibition measured (two diameters normal to each other).…”