FERMENTATION OF AMINO ACIDS BY MICROCOCCUS AEROGENES

Abstract

Quantitative data for the fermentation of serine, threonine, glutamate and histidine by strain 228 of M. aerogenes are presented. A "Stickland reaction" does not occur in this strain or in any of the related anaerobic micrococci. Serine is degraded to NH3, CO2, H2, and acetate with pyruvate as an intermediate product. Deamination of serine is stimulated by pyridoxal phosphate but not by biotin, glutathione, adenylic acid or combinations of these cofactors. Threonine is fermented to NH3, CO2, H2, and propionate, with [alpha]-ketobutyrate as an intermediate. Glutamate is degraded to NH3, CO2, H2, acetate and butyrate. Mesaconate, citramalate and a-ketoglutarate are not formed from glutamate or degraded by any preparation of M. aerogenes. Histidine is fermented to NH3, CO2, acetate, butyrate, lactate, and traces of formate, with urocanate as an intermediate product. A comparison of end-products, as well as other experimental evidence, indicate that if glutamate is formed as an intermediate product in histidine fermentation, its subsequent degradation is different from that of exogenously supplied glutamate.