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Abstract
SUMMARY: Nutritional experiments were carried out dealing with (1) the utilization of sulphur compounds; (2) the action of different mineral salts and their interaction. The results showed that the species of Phyhium used grew well at 28° buffered with Sorensen’s salt to give an initial pH of 6.5 and incubated for 13 days for Pythium afertile and 10 days for the remaining species. Acid conditions below pH 5.0 and alkaline conditions above pH 8.0 were not tolerated. The best carbon and nitrogen sources are given. The best sulphur sources were Na2S. Na2S2O3, Na2S04. 10 H2O, Na2SO3.7H2O, Na2S2O5.5H2O, K2S2O8, molecular sulphun. DL-methioninee thioacetamide, L-cysteine, sodium thioglycolate, and DL-cystine Factorial experiments were carried out in which the fungi were incubated at 28° for 13--14 days. Statistical analysis of the results showed that under the given conditions optimal growth measured as mg. dry wt. was obtained in liquid media containing glucose, 10.0 g./1.; KCl. 0.5 g.l with varying amounts of K2HPO4, KNO3 and MgSO4. 7H2O for the different species specified. There was a balance between K2HPO4 and MgSO4. 7H2O for P. debary-anum and there were significant interactions between the salts above taken two at a time for P. debaryanum and P. ultimum but the interactions for the remaining fungi were more variable. There was interaction between all three salts together for two of the species. P. debarganum is more exacting in its nutritional requirements than the other species.
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