Description:
<jats:p>Mutants of <jats:italic>Escherichia coli</jats:italic> (pdx B and pdx C) which are blocked in the biosynthesis of pyridoxol (vitamin B<jats:sub>6</jats:sub>) showed a growth response to 4‐hydroxy‐<jats:sc>l</jats:sc>‐threonine. This observation constitutes the first direct evidence in support of the view that 4‐hydroxy‐<jats:sc>l</jats:sc>‐threonine is implicated in the biosynthesis of vitamin B<jats:sub>6</jats:sub>. 1‐Aminopropan‐2,3‐diol, the decarboxylation product of 4‐hydroxy‐<jats:sc>l</jats:sc>‐threonine, does not support the growth of these mutants. Deuterium from deuterium‐labelled 1‐aminopropan‐2,3‐diol was not incorporated into pyridoxol.</jats:p>