Abstract
E. coli KG 980,a vitamin B_6 auxotroph, could not utilize for its growth three phosphate forms of vitamin B_6 at the concentrations ranging from 10^<-7>M to 10^<-5>M in the minimum medium of Davis and Mingioli supplemented with glucose. The bacterium, however, utilized the phosphate forms in the phosphate starving medium of Garen and Levinthal which is known to derepress alkaline phosphatase, and it grew well on 10^<-6>M pyridoxine phosphate, 10^<-6>M pyridoxal phosphate or 10^<-5>M pyridoxamine phosphate. Correspondingly, the bacterial cells grown in the minimum medium could not take up the phosphate esters of tritium labelled vitamin B_6 compounds at 10^<-6>M concentrations in the same medium, whereas the cells grown in the phosphate starving medium significantly took up the labelled compounds in the same medium. The main labelled vitamin B_6 compound in the phosphate starving medium after 30-min incubation of labelled pyridoxine phosphate with the cells grown in the same medium was found to be pyridoxine. Furthermore, uptake of the labelled pyridoxine phosphate by E. coli K 12 cells was essentially similar to that by E. coli KG 980 cells. These results indicate that the phosphate forms of vitamin B_6 can be taken up and utilized after de phosphorylation by alkaline phosphatase, but not taken up in their intact form.
