Role of Vitamin B 6 Biosynthetic Rate in the Study of Vitamin B 6 Synthesis in Escherichia coli

Abstract

Nutritional auxotrophs of Escherichia coli synthesize vitamin B 6 compounds at a rate of 1 × 10 −10 to 2 × 10 −10 moles per hr per mg (dry weight) of cells when they are suspended in minimal medium lacking their required nutrients. A few auxotrophs have been found to stop or reduce vitamin B 6 synthesis during such an experiment. These include thiamineless, citrate synthaseless, and pyridoxineless mutants as well as mutants which require four carbon compounds for growth. Glycolaldehyde was found to restore vitamin B 6 synthesis in the last named of these mutants without restoring normal growth. A class of pyridoxineless mutants which responded with normal growth to 0.4 m m glycolaldehyde or 0.15 × 10 −3 m m pyridoxol was also found. The results suggest that a thiamine pyrophosphate-requiring step as well as glycolaldehyde may be involved in pyridoxal phosphate biosynthesis.