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Abstract
SUMMARY: When incubated with p-aminobenzoic acid, formate and glucose, suspensions of a variant strain of Leuconostoc mesenteroides strain P60 formed two factors possessing folic acid activity. One of these factors behaved like rhizopterin in supporting the growth of Streptococcus faecalis strain R but not of Lactobacillus casei. The other, like leucovorin, supported the growth of Leuconostoc citrovorum. The synthesis of ‘citrovorum factor’ was enhanced 5- to 20-fold by the presence of CO2 in the gas phase. Sulphathiazole inhibited the synthesis of both factors, the inhibition being overcome competitively by p-aminobenzoic acid. Leucovorin was destroyed by suspensions of L. mesenteroides P60 in phosphate-buffered glucose. The diminution of activity for L. citrovorum (decrease of citrovorum factor) was decreased when the incubation was carried out in a CO2-enriched atmosphere. Ascorbic acid, which behaved similarly to CO2 in partially preventing inactivation of leucovorin by suspensions of L. mesenteroides P60 variant strain, also increased the synthesis of citrovorum factor from formate and p-aminobenzoic acid and partially satisfied the requirement of the growing L. mesenteroides P60 for CO2.
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