Of 38 pure cultures of microorganisms tested, only one, Pseudomonas stutzeri, was capable of forming dimethylnitrosamine from dimethylamine and nitrite during growth. Resting cells of P. stutzeri, Cryptococcus terreus, Escherichia coli, and Xanthomonas campestris formed dimethylnitrosamine, although no nitrosamine was found in growing cultures of the latter three organisms. No nitrosamine was produced by either growing cultures or resting-cell suspensions of Pseudomonas fragi or Proteus mirabilis. Boiled cells of P. stutzeri, but not those of C. terreus, E. coli, and X. campestris, formed dimethylnitrosamine, and this nitrosamine was also produced by extracts of E. coli cells at pH 5.0.
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