Abstract
SUMMARY: Thirty-eight methods or modifications of methods for removing trace metals from nutrient media were tested, using Aspergillus niger as test organism to indicate deficiencies. The most marked symptoms of Zn and Fe deficiencies were obtained after treatment by the Al2O3 or dithizone + oxine methods, of Cu and Mn deficiencies by the Al2O3 method, and of Mo deficiency by Nicholas's method which involves co-precipitation with sulphides of Cu and Pb. Four strains of A. niger differed in their trace element requirements. Shake cultures of A. niger gave less growth in complete medium than did surface cultures, while in deficient media this was reversed. Sucrose peptone and broth media were only partially purified by the Al2O3 treatment. Deficiencies of Fe, Zn and Cu were obtained for Chlorella vulgaris, and of Fe and Zn for Torulopsis utilis, as detected by growth response. Apart from decrease of growth, trace metal deficiency symptoms in Penicillium roqueforti were not very obvious.
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