Some Observations on Growth Factors Required by Leuconostoc citrovorum. ∗

Abstract

Summary

1. Leaconostoc citrovorum was found to respond to a growth-promoting factor in the concentrated liver extract, but this organism did not respond to vitamin B₁₂. The alkali-stable nature of the “citrovorum factor” further contrasts it with vitamin B₁₂. 2. Two fractions were separated from liver extract by paper strip chromatography; one of these fractions was presumably thymidine and promoted growth of Lactobacillus leichmannii and Leuconostoc citrovorum. The other fraction was inactive for L. leichmannii but active for L. citrovorum.

3. Although thymidine or high levels of pteroylglutamic acid (PGA) when tested singly were only partially effective in promoting growth of L. citrovorum, the simultaneous addition of thymidine plus PGA produced marked growth of the organism. This finding suggests a functional relationship between thymidine, PGA and the “citrovorum factor.”