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Appl Environ Microbiol. 1989 March; 55(3): 649-655
Northern Regional Research Center, U.S. Department of Agriculture, Peoria, Illinois 61604.
ABSTRACT
The influence of zinc, iron, cobalt, and manganese on submerged cultures of Fusarium moniliforme NRRL 13616 was assessed by measuring dry weight accumulation, fusarin C biosynthesis, and ammonia assimilation. Shake flask cultures were grown in a nitrogen-limited defined medium supplemented with various combinations of metal ions according to partial-factorial experimental designs. Zinc (26 to 3,200 ppb [26 to 3,200 ng/ml]) inhibited fusarin C biosynthesis, increased dry weight accumulation, and increased ammonia assimilation. Carbohydrate was found to be the principal component of the increased dry weight in zinc-supplemented cultures. Zinc-deficient cultures synthesized more lipid and lipidlike compounds, such as fusarin C, than did zinc-supplemented cultures. Microscopic examination showed that zinc-deficient hyphae contained numerous lipid globules which were not present in zinc-supplemented cultures. Addition of zinc (3,200 ppb) to 2- and 4-day-old cultures inhibited further fusarin C biosynthesis but did not stimulate additional dry weight accumulation. Iron (10.0 ppm) and cobalt (9.0 ppm) did not affect fusarin C biosynthesis or dry weight accumulation. Manganese (5.1 ppm) did not affect dry weight accumulation but did increase fusarin C biosynthesis in the absence of zinc. Maximum fusarin C levels, 32.3 micrograms/mg (dry weight), were produced when cultures were supplied manganese, whereas minimum fusarin C levels, 0.07 micrograms/mg (dry weight), were produced when zinc, iron, cobalt, and manganese were supplied. These results suggest a multifunctional role for zinc in affecting F. moniliforme metabolism.
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