SULFUR METABOLISM IN ESCHERICHIA COLI II

Abstract

Metabolism of S35 labeled Na2SO4,cystine or methionine in the presence of various nonlabeled sulfur compounds demonstrates a number of preferential sequences in the utilization of sulfur. Sulfite, thiosulfate, lanthionine and cyst(e)ine completely eliminate radiosulfate uptake, homocyst(e)ine and methionine cause a depression while cysteic acid, taurine, thiourea, cystathionine and djenkolic acid have no effect. Lanthionine, homocyst(e)ine and methionine depress radiocystine utilization. None of the compounds tested affects the uptake of radiomethionine. Since the utilization of radiocystine could not be completely suppressed, it is suggested that at least 2 pathways exist in the metabolism of cystine. Methionine appears to be directly incorporated into protein. The data demonstrate that changes in the sulfur environment of E. coli result in altered biochemical reactions in the metabolizing cell while the simultaneous use of labeled and nonlabeled sulfur sources provide a means by which the biochemical relationship between the bacterial cell and its environment may be evaluated.