Factors which govern toxin production by type A were studied in growing cultures and in non-proliferating cell suspensions. With growing cultures high toxin titres, comparable to those obtained in complex media, were obtained in a defined medium containing the following essential constituents: arginine, cysteine, histidine, isoleucine, leucine, methionine, phenylalanine, serine (or glycine), tyrosine, tryptophan, valine, glucose, vitamins, phosphate and magnesium. Most of the toxin was formed only after cessation of growth.

Resting suspensions of organisms produced toxin at a rapid rate; a three- to fivefold increase being obtained after 4 hr. incubation. It appears that the toxin is synthesized within the organisms and is liberated into the medium by autolysis. Release of toxin on artificial lysis by sonic oscillation, provided decisive evidence for this conclusion.

The effect of different metabolic inhibitors on toxin synthesis by resting organism suspensions was examined. Ethylenediamine tetracetic acid in amounts which did not inhibit growth suppressed completely toxin production. Some broad spectrum antibiotics (streptomycin, chloramphenicol, chlorotetracycline at 100μg./ml.) inhibited toxin formation to about 50%. Penicillin did not affect toxin synthesis even at concentrations 1000-fold higher than those required to arrest growth of the organism.


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