A transgenic bacterial host cell that can be used as a screen for novel antibiotics and herbicides is provided. The genome of the transgenic bacterial host cell comprises disruptions in a first endogenous gene in the MEP pathway) and a transgene that functionally replaces the disrupted first gene. In other embodiments, the genome comprises a disruption in a first endogenous gene in the MEP pathway and a second endogenous gene which is located downstream of the first gene in the MEP pathway. A transgene that functionally replaces the disrupted downstream gene is cloned into the host cell. A mini operon containing the essential genes for the MVA pathway may also be cloned into the host cell. The transgenic host cell may be used in a method for screening compounds for antibiotic and herbicidal properties. The agents determined by the screening method may be used to kill bacteria or plants.