TOXICITY OF ELEMENTAL SULFUR FOR BRUCELLAE

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Abstract
Previous investigations demonstrated that autoclaved cystine effects marked growth inhibition of certain Brucella spp. Filtered cystine is nontoxic. Toxic monoclinic sulfur crystals were isolated from autoclaved cystine soln. by adsorption on norit and elution with pyridine. Sterile, colloidal dispersions of elemental S in concns. as low as 0.06 [mu]g./ml. inhibited growth of brucellae when added aseptically to the basal media. The toxicity of elemental S was reversed by the same agents which neutralize cystine and tryptose toxicity. Freshly autoclaved cystine solns. contain cysteine, H2S, elemental S, ammonia, and pyruvic acid. It is believed that a preliminary dismutation of a fraction of the cystine to cysteine is followed by degradation of the latter to pyruvate, ammonia, and H2S by way of an unstable imino acid. The H2S in turn reacts with excess cystine to form toxic S and additional cysteine. This reaction may be reversed, with consequent elimination of S induced toxicity, by adding excess sulfhydryl compound to the system.