The nature of some growth stimulatory substances for Lactobacillus delbrueckii.

In addition to the usual amino acids and vitamins, Lactobacilus delbrekii strain 730 (ATCC 9649) has been shown to require pyridoxamine phosphate (McNutt and Snell, 1950), thymidine (Kitay, et al., 1950), and an unsaturated fatty acid (e. g., oleic acid) (Kitay and Snell, 1950) for growth. In addition to these absolute requirements for growth, partial acid hydrolyzates of casein further stimulate growth of this organism. This stimulation has been duplicated by the addition of histidine and serine peptides (Peters et al., 1953; Prescott et al., 1953) to the growth medium. Details of the nutritional requirements of L. delbrueckii strain 730 have recently been reported by Peters and Snell (1954). When the organism is grown in the presence of all of these substances, the time required for maxmum growth to occur is reduced substantially by the addition of an enzymatic hydrolyzate of casein or a variety of natural extracts. This effect is especially noticeable when a short incubation period and a very dilute inoculum are employed. The nature of some of these additional growth stimulatory factors for L. delbrueckii is reported in this paper.