Polyamines of thermophilic moulds: distribution and effect of polyamine biosynthesis inhibitors on growth

Abstract

Putrescine (Put), spermidine (Spd) and spermine (Spm) were widely distributed in 15 thermophilic moulds representing Zygomycetes, Ascomycetes, and Deuteromycetes. However, Put was only sporadically distributed in the members of Zygomycetes. Appreciable amounts of cadaverine (Cad) were found in most of the fungi. Certain members of Ascomycetes and Deuteromycetes contained one/two unidentified polyamines (PAs). Temperature and age of the culture had marked effect on endogenous free pool of PAs in Humicola lanuginosa. Polyamine levels declined at temperatures below and above the optimum (45 °C). The concentration of PAs was greater in actively growing mycelium than that in old cultures. Difluoromethylomithine (DFMO), a specific and irreversible inhibitor of ornithine decarboxylase (ODC), strongly inhibited mycelial growth of H. lanuginosa, Talaromyces emersonii and Mucor pusillus. However, each fungus had a different response pattern. Spermidine at 1·0 m m totally prevented the inhibitory effect of DFMO in H. lanuginosa. Difluoromethylarginine (DFMA), an inhibitor of arginine decarboxylase (ADC), at 1·0 m m had no effect on these moulds except in M. pusillus where mycelial growth was considerably reduced. Since these results suggest that PAs are required for normal growth of thermophilic moulds, DFMO and other PA biosynthesis inhibitors can be used as protectants against diseases and biodeterioration caused by these moulds.