Abstract
This paper deals with the comparison of the effects of cyanocobalamin and hydroxocobalamin on the syntheses of acid-soluble deoxyribosyl compounds and DNA in vitamin B_<12>-starved cells of Lactobacillus leichmannii grown on a medium containing deoxyguanosine instead of vitamin B_<12>. The ratio of DNA to RNA in the cells was significantly lower than that of normal cells. The cell elongation was not recognized. contrary to an usual vitamin B_<12> starvation. The incubation of the cells in a medium containing cyanocobalamin, hydroxocobalamin or DBCC permitted a remarkable increase of acid-soluble deoxyribosyl compounds followed by DNA synthesis without the increase of RNA content as well as the growth. Hydroxocobalamin exerted a greater effect than cyanocobalamin. DBCC exogenously added showed almost the same activity as that of hydroxocobalamin being inconsistent with the authors' observation that vitamin B_<12>-group compound derived from external cobalamins in the cells seems to be identical with DBCC or a closely related substance. The reason might be attributed to splitting of the deoxyadenosyl ligand from DBCC molecule when it is uptaken into the bacterial cells.
