New factors in the nutrition of Lactobacillus casei.

Studies of the nutritive requirements of the bacterium, Lactobacillus casei, have contributed much to our present knowledge of animal nutrition. It appears that the vitamin requirements of this microorganism are very similar to those of animals. Landy and Dicken (1) reported a microbiological assay method for six B vitamins with Lactobacillus casei and a medium of essentially known composition. This work indicated that the vitamin requirements of L. casei were met by inclusion in the growth medium of riboflavin, biotin, pantothenic acid, pyridoxine, nicotinic acid, and folic acid. This method of assay was found to work successfully in many laboratories. However, in some laboratories good growth of L. casei could not be obtained on this medium. Pollack and Lindner (2) reported a growth stimulant for Lactobacillus casei which was present in Wilson’s peptone. They reported that glutamine was capable of replacing the peptone factor, but that glutamine itself could not be identical with the active factor in peptone since it is easily dest.royed by mild alkaline hydrolysis while the factor in peptone is not. Woolley (3) reported that certain hemolytic streptococci require an unknown factor for growth. Later, Sprince and Woolley (4) found that, under certain conditions, this factor is also required by a variety of bacteria, including Lactobacillus casei. These workers have tentatively named the factor strepogenin. Sprince and Woolley (5) have found strepogenin to be an integral part of certain purified proteins from which it can be freed most efficiently by incubation with trypsin. Their studies of the properties of this factor have led them to suggest that it may be a peptide. They have reported that strepogenin is dialyzable after trypsin digestion, that it is destroyed by acid hydrolysis, and that it is adsorbed to some extent by barium sulfate, but not by charcoal.