The Growth Factor Requirements of Certain Streptococci

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Abstract
The recent report of Niven that asparagine is effective in promoting growth of Streptococcus lactis is confirmed. Purified glutamine was ineffective in lieu of asparagine. Neither asparagine nor glutamine, nor a combination of the 2, was effective in stimulating the growth of a strain of Str. fecalis. In the absence of asparagine and glutamine, trypsinized vitamin-free casein is effective in promoting growth of both Str. lactis and Str. fecalis. In the case of Str. lactis, the activity of the casein digests in promoting growth is much greater than can be accounted for on the basis of the aspartic (or glutamic) acid content of casein. Obviously a factor or factors more highly active than asparagine (or glutamine) must be present. Asparagine (or glutamine or both) may suffice as growth factors for certain streptococci but they are involved in the structure or synthesis of more highly active compounds which function in the nutrition of the more fastidious strains.

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