NITROGENOUS COMPOUNDS AS SUBSTRATES FOR ENDOGENOUS RESPIRATION IN MICROORGANISMS

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Abstract
In an effort to establish the relative importance of nitrogenous compounds as endogenous substrates nine microorganisms were tested for their ability to produce ammonia during endogenous respiration. Pseudomonas aeruginosa, Pseudomonas fluorescens, Achromo-bacter species, Escherichia coli, Bacillus subtilis, Saccharomyces cere-visiae, and Streptococcus faecalis consistently produced appreciable quantities of ammonia. The strain of Aerobacter aerogenes used produced no detectable quantities of ammonia. When glucose was added to respiring cell suspensions, all organisms except S. faecalis reincorporated the accumulated ammonia. When the ratio of oxygen consumedto ammonia evolved was determined, it was found that the pseudomonads consistently had values of 4.5, indicating that the endogenous substrates could have been proteins which had been oxidized to completion. The ratios for B. subtilis and S. faecalis were lower, indicating that the endogenous substrates contained a high percentage of nitrogen or that the substrates were incompletely oxidized. The other organisms gave values greater than 4.5, indicating that non-nitrogenous compounds were also serving as endogenous substrates for these organisms.