The microcins are a class of antimicrobial peptides produced by Gram-negative bacteria that putatively function to give the producing cell a selective advantage during periods of stress or nutrient depletion. One of these peptides, microcin J25 (MccJ25) has received attention due to its unusual lasso structure which imbues it with extraordinary thermal stability. Consistent with its ecological role, however, the production of MccJ25 is initiated only during stationary phase, limiting the yield of active peptide to only several milligrams per liter of bacterial culture. To improve the yield of MccJ25, we have reengineered the gene cluster responsible for the expression and maturation of the peptide. Preliminary data indicate significantly improved yields of MccJ25 in our engineered system relative to natural producer cells. This improved system for the production of MccJ25 also serves as a platform for the engineering of the peptide for improved and novel functions.