SUMMARY: A Penicillium species isolated from soil, decomposed up to 0·1% (w/v) thiourea only with an energy source such as glucose. The fungus released part of the sulphur and nitrogen as sulphate and ammonia which served as S and N sources. The medium became strongly acid due to organic acids originating from glucose; at the acid reactions the amount of sulphate formed was small, but near neutrality most of the sulphur was oxidized to sulphate. Most decomposition of the thiourea and production of sulphate and acid occurred during the lag phase. Ammonium nitrogen promoted growth but reduced decomposition of thiourea. Nitrate was assimilated in the absence of thiourea but not in its presence. Citrate did not support growth but promoted assimilation of nitrogen. Glucose augmented from 0·2 to 2·0% led to increased growth, decomposition of thiourea and production of sulphate and acid. Aeration also promoted growth and sulphate production. Among the incompletely oxidized decomposition products were sulphate esters and ureides.

Sulphate production indicated that thiourea and four substituted thioureas underwent slow decomposition in soil and sewage sludge. In soil, all of the sulphur of the compounds was oxidized to sulphate in 20 weeks; decomposition was much slower in sewage sludge. Most cultures isolated from treated soil and sewage sludge failed to attack thiourea in culture media on serial transfer.


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