SULFUR METABOLISM IN ESCHERICHIA COLI IV

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Abstract
While methionine has been shown to be essential for the growth of methionine-requiring mutant (1-344) strain 15 E. coli cells, the metabolism of non-methionine S added to media containing methionine has not been investigated directly. Observations of some of the metabolic reactions occurring on either side of the biochemical block have indicated the interrelationship existing between the required utilization of methionine and the metabolism by non-methionine S. Either 2-C 14 or S35 labeled methionine as the sole S source in the medium permitted less than max. cellular growth. Radiocystine could not be detected in acid hydrolysates of these cells and radiomethionine appeared to be the only S-containing amino acid upon chromatographic analysis. Radiocystine but not radiomethionine was observed when radiosulfate and non-radioactive methionine were both present in the medium, Non-methionine S was shown to be necessary for max. growth, and variation in S content of the cells was shown to occur due to reduced cystine production in the cell as the sulfate content of the medium was reduced. No alteration of the cellular methionine content was observed over a variety of S environments.