Microbial metabolism of carbamates. II. Nitrification of urethan by Streptomyces nitrificans.

The inhibition of hexokinase (Meyerhof and Wilson, 1948), choline oxidase (Goldfinger et al., 1947), and other enzyme systems by urethan and related carbamates has been studied extensively. Yet precisely how these compounds exert their physiological effects is unknown. Warburg (1921) considered urethan to be an "indifferent" narcotic, blocking dehydrogenases by nonspecific absorption on cellular interfaces. Inhibition of yeast respiration by urethan has been attributed to its behavior as a nonionic surface active agent (Lamanna and Campbell, 1953). This carbamate also inhibits the antibacterial action of low levels of sulfonamides (Johnson et al., 1943) and causes a decrease in the catalase content of Escherichia coli (Pontieri, 1953). The antagonism of the leucopenic and carcinogenic properties of urethan by pentose nucleotides (Cowen, 1949) and the reversal of urethan inhibition of E. coli by 2,6-diaminopurine (Skipper and Schnabel, 1952) suggest an interference with nucleic acid metabolism. The over-all objective of the present studies was to compare the intermediary metabolism of microorganisms grown with and without carbamates as substrates. Such information, it is believed, may prove useful in elucidating the physiological mode of action of these compounds. For this purpose, cultures capable of developing on carbamates were isolated from various sources by suitable enrichment techniques (Schatz et al., 1954). This report deals with the unusual nitrifying ability of Streptomyces nitriians, a heterotrophic organism that can utilize urethan as the sole source of nitrogen, carbon, and energy.