The relation of serine-glycine metabolism to the formation of single-carbon units

Cultivation of serine-glycine auxotrophs of Escherichia coli in a medium containing serine and a purine base results in a temporary inability of the cells to grow upon transfer to a medium containing glycine as the nutrilite. It could be shown that this failure to grow is due to the inability of the cells to obtain single-carbon units from glycine. The formation of the enzyme system required for the synthesis of single-carbon units from glycine seems to be controlled through repression exerted by the intracellular single carbons. The intracellular concentration of single-carbon units derived from the β-carbon of serine is apparently increased by the addition of a purine base to the growth medium.