Arginine, a growth-limiting factor for Eubacterium lentum

Eubacterium lentum is a gram-positive, asaccharolytic, obligately anaerobic bacillus, which grows to a low turbidity (absorbancy at 650 nm = 0.05 to 0.1) in peptone-based medium. The addition of substrate amounts of arginine or citrulline dramatically increased growth (absorbancy at 650 nm =1.4). The presence of an arginine dihydrolase pathway was confirmed by measurement of the necessary enzymes and demonstration of the intermediate compounds. The production of adenosine 5'-triphosphate from the arginine dihydrolase pathway appeared to be the sole source of energy for growth of this organism. Each of 11 strains showed definite growth stimulation. Ten of the 11 strains had cytochromes. Growth stimulation with arginine and the presence of cytochromes offer two new positive criteria for the identification of E. lentum.