The present invention features improved processes and organisms for the
production of methionine. The invention demonstrates that a .DELTA.metF
organism or a .DELTA.metE AmetH organism, for example, mutants of C.
glutamicum or E. coli, can use a methyl capped sulfide source, e.g.,
dimethyl disulfide (DMDS), as a source of both sulfur and a methyl group,
bypassing the need for MetH/MetE and MetF activity and the need to reduce
sulfate, for the synthesis of methionine. Also described in this patent
are data implicating MetY (also called MetZ) as an enzyme that
incorporates a methyl capped sulfide source, e.g., DMDS, into methionine.
A .DELTA.metF .DELTA.metB strain of C. glutamicum can use a methyl capped
sulfide source, e.g., DMDS, as a source of both sulfide and a methyl
group. Furthermore, methionine production by engineered prototrophic
organisms that overproduce O-acetyl-homoserine was improved by the
addition of a methyl capped sulfide source, e.g., DMDS.