Stilbella thermophilaFergus was grown on a chemically denned medium ofD-glucose, KNO3, MgSO4, KH2PO4, agar, and microelements to determine the effect of environment and nutrition on growth and synnemata production. An exogenous supply of thiamine stimulated growth markedly on pyridine-purified agar, but both thiamine and biotin were required for synnemata to form. Pyrimidine was the effective moiety, not thiazole.S.thermophilagrew on a large number of carbon and nitrogen compounds substituted singly into the basal medium, but synnemata formed on less than half of such media. Sucrose did not inhibit synnemata formation with glucose present, but no synnemata formed with sucrose in the medium even with a number of different nitrogen sources. Synnemata production followed chance mold contamination on a few of the media that normally did not allow their production. The carbon–nitrogen ratio significantly affected synnemata formation. So did pH, concentration of phosphate buffer, and temperature. At suboptimal temperatures, reduced synnemata, or only loose bundles of conidiophores, formed. Light was not required for synnemata initiation nor for maturation. Synnemata formation occurred over a narrower range of temperature, pH, vitamin concentration, nutrient concentration, and nutrient spectrum (carbon and nitrogen sources) than did mycelial growth.
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