Control of Vitamin B 6 Biosynthesis in Escherichia coli

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Abstract
Pyridoxineless mutants of Escherichia coli B which specifically require pyridoxal or pyridoxamine for growth can be divided into classes according to their growth responses in enriched media. Members of the slowest growing class synthesize vitamin B 6 at the fastest rates when starved for pyridoxal in glycerol minimal medium. After 80 min of synthesis at 4 × 10 −10 moles of vitamin B 6 per mg of cells per hr, the rate increases four- to fivefold and continues at the new rate for several hours. The shift to the new rate is prevented by chloramphenicol, thus suggesting that a derepression mechanism exists to control vitamin B 6 synthesis in addition to the previously discovered feedback control.