Probable identity of the growth promoting factor for Butyribacterium rettgeri with other biologically-active substances.

Kline and Barker (1950) reported the existence and some properties of an apparently new unidentified growth factor (B.R. factor) required by Butyribacterium rettgeri for growth on lactate as the fermentable carbon source. Certain similarities in properties were given as the basis for a postulated relationship of the B.R. factor to other unidentified growth or metabolically active substances. These related factors included: (a) the acetate replacing factor reported by Guirard, Snell, and Williams (1946) as stimulatory for the early growth of Lactobacillus casei; (b) the pyruvic oxidase factor reported by O'Kane and Gunsalus (1947, 1948) as necessary for activation of the apo-pyruvic oxidase of Streptococcus faecalis; and (c) a factor necessary for the growth of Tetrahymena geleii caled protogen by Stokstad et al. (1949) who reported some of its properties. Stokstad et al. (1950) later reported that protogen was also necessary for the growth of an unidentified C(nebacterium. Snell and Broquist (1949) presented evidence for the interchangeability of these three latter activities. They reported that concentrates, purified with respect to pyruvic oxidase activity and having activities of 1, 70, and 3,000 pyruvic oxidase units per mg, had relative acetate replacing activity for L. cacsei of 1, 90, and 3,300, respectively. They also showed that a protogen preparation purified 10,000-fold over the source material as indicated by Tetrahymena assay was highly active for L. casei; 3 mug of this preparation were equivalent to the growth promoting activity of 400,ug of sodium acetate. The purpose of this report is to present further evidence on the relation of the B.R. factor to the three activities previously related by Snell and Broquist (1949).