590 NEW AND UNIDENTIFIED GROWTH FACTORS 



water and added aseptically to a sterile yeast-casein medium. Heating of 

 glucose with the medium resulted in normal growth, as did heating of small 

 amounts of methylglyoxal, furfural, or pentoses with the yeast-casein mix- 

 ture. These observations have been repeated and extended in later 

 years, '^*"'" so that it appears.that at least two types of transformation occur 

 during heating: one is the expulsion of oxygen and/or the formation of re- 

 ducing substances, "'^^ ii'^i'i whereas the other involves interaction of car- 

 bohydrate with phosphate and/or the nitrogenous components of the me- 

 dium. The compounds so produced were presumed to act as the stimulatory 

 agents. 



Studies in this laboratory^-^ have revealed that products formed by heat- 

 ing glucose with inorganic phosphate and amino acids will greatly stimu- 

 late the growth of Lactobacillus gayoni 8289 (strain 45; cf. ref. 123 for de- 

 scription of organism) during a 12-hour incubation period. In a series of 

 experiments, glycine was found to be consistently superior to other amino 

 acids as a precursor of active material, whereas alanine produced substances 

 that were strongly inhibitory. N-Glucosylglycine was then synthesized as 

 the ethyl ester^^* and found to be as active as equal weights of yeast extract 

 in a filter-sterilized medium, at levels up to 1 mg. per 10 ml. of culture. 

 Higher levels of yeast produced greater stimulation, whereas amounts of 

 glucosylglycine above 5 mg. became inhibitory. However, when glucosyl- 

 glycine was heated separately and added aseptically to the basal medium, 

 additional growth stimulation was provided which approached, although 

 it did not equal, the growth on yeast extract. Of approximately twenty 

 species of lactic acid bacteria tested, three others w^ere stimulated by un- 

 heated glucosylglycine: Streptococcus zymogenes 10100, Lactohacillus acido- 

 philus (O.S.C. strain), and Leuconostoc mesenteroides P63. L. gayoni F20 

 responded only after the compound had been heated. Other organisms, 

 such as L. gayoni 8289, strain 49,^^^ L. casei, and Saccharomyces cerevisiae 



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