The fermentation of amino acids by Micrococcus aerogenes

The anaerobic micrococci described by Foubert and Douglas (1948a) may be divided into 3 groups on the basis of ability to degrade organic compounds: (1) those capable of fermenting only glycine (Douglas, 1951), (2) those able to degrade purines (Whiteley and Douglas, 1951) and many organic acids (Foubert and Douglas, 1948b), and (3) those able to ferment purines and a limited number of amino acids and organic acids. To the first group belong the species Micrococcus vari-abilis and Micrococcus anaerobius, to the second, Micrococcus lactilyticus (also called Veillonella gazogenes), and to the third, Micrococcus aero-genes, Micrococcus prevotii, Micrococcus activus, and Micrococcus asaccharolyticus. A survey of nine strains belonging to the third group has shown that serine, threonine, histidine, glutamic acid (and glutamine), pyruvate, a-ketobutyrate and urocanate are fermented. Although the strains vary considerably, each compound is degraded by at least one strain of each species, and all are fermented by strain 228 of M. aero-genes. The fermentation of purines by this strain has been described (Whiteley, 1952). This com-munication presents the results of studies on the fermentation of amino acids and a discussion of the mechanisms of degradation by M. aerogenes. METHODS Cells were grown either in the peptone-yeast extract medium ("peptone medium") described previously (Whiteley, 1952) or in the same medium supplemented with 0.4 per cent sodium glutamate ("glutamate medium"). The gluta-mate medium supports a more rapid rate of growth, and yields cells capable of fermenting all substrates at a high rate. Since such cells have a considerably higher rate of endogenous metabo-ism, both media were used depending on experi-mental needs. Conditions of growth, harvesting