Identification of the forms of vitamin B 6 present in the culture media of "vitamin B 6 control" mutants.

An Escherichia coli mutant resistant to isoniazid (WG497) contained 0.6 mumole of extracellular pyridoxamine and pyridoxamine phosphate in the early stationary phase. A suppressed lysine mutant (AT1024) contained 1.4 mumoles of pyridoxal phosphate under the same conditions. The internal concentration of vitamin B(6) was one-half of normal for AT1024 and increased fivefold for WG497.