N-Nitrosamine formation by cultures of several microorganisms

Abstract

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.

Distribution and metabolism of ingested NO3- and NO2- in germfree and conventional-flora rats

“…The end product(s) of these microbial reductions of N03 and NO2was not identified. Other investigators have found bacteria capable of forming N-nitroso compounds, from the precursor compounds, both in vitro (5,20) and in vivo (11); however, the amounts formed were low. This suggests that some other compounds, such as ammonia, could be formed in the CV intestinal tract.…”

“…Under conditions that exist in the human gastrointestinal (GI) tract (6,18,35), infected urinary bladder (4,13), or achlorhydric stomach (29,30), nitrites (or nitrates after reduction) can react with certain primary, secondary, tertiary, and quaternary amines or amides to produce the corresponding nitrosamines or nitrosamides. This nitrosation reaction is catalyzed either by acid conditions, as found in the nonnal stomach, or by certain bacteria under more neutral or alkaline conditions (20,21). Most nitrosamines and nitrosamides are extremely potent and efficient carcinogens (19,28).…”

Nitroalkane Oxidation by Streptomycetes

“…Assuming that the S. achromogenes enzyme that we have studied, despite its high Km for 2nitropropane, is a genuine nitroalkane-oxidizing enzyme and given the widespread occurrence of nitroalkane-oxidizing activity in strains of Streptomyces as well as the relative ease of formation of N-nitroso compounds (5,22), it appears that the potential of a strain to produce a compound containing an N-N bond might be governed by the availability of a suitable aliphatic nitro compound within the cells of that strain. Streptomycetes elaborate a variety of compounds containing nitro groups (16), but the only one known to contain a primary nitro group is 3-nitropropionic acid (bovinocidin [1]).…”

“…It is conceivable that nitrous acid may participate in biological N-N bond formation. This assumption is based on the fact that nitrous acid is a well-recognized reagent in organic chemistry used to effect N-N bond formation, and it is supported by experiments on N-nitrosamine formation from a variety of amines and sodium nitrite by intact bacteria (32) and by bacterial cell-free extracts (5,22). On the basis of these microbiological studies, it appears that nitrosation might proceed quite readily either as an enzyme-catalyzed process or possibly as an or-ganic matter-catalyzed process (5,22), provided that nitrous acid can be generated within the respective cells.…”

“…This assumption is based on the fact that nitrous acid is a well-recognized reagent in organic chemistry used to effect N-N bond formation, and it is supported by experiments on N-nitrosamine formation from a variety of amines and sodium nitrite by intact bacteria (32) and by bacterial cell-free extracts (5,22). On the basis of these microbiological studies, it appears that nitrosation might proceed quite readily either as an enzyme-catalyzed process or possibly as an or-ganic matter-catalyzed process (5,22), provided that nitrous acid can be generated within the respective cells. Two main pathways that can lead to the formation of nitrous acid have been reported in microorganisms: reduction of inorganic nitrates (26) and degradation of organic nitro compounds (6,9,12,17,23,33).…”