Compositions and methods for controlling genetically engineered organisms

A microorganism, comprising a streptavidin gene under control of a first heterologous promoter, wherein said streptavidin gene is by a heterologous RNA polymerase, said RNA polymerase expressed from a RNA polymerase gene under control of a second heterologous promoter, said second heterologous promoter inhibited by the expression of a repressor protein from a repressor gene, said repressor gene is under the control of a third heterologous promoter and operably linked to nucleic acid encoding antisense RNA complementary to at least a portion of said streptavidin gene, said repressor protein expressed by said microorganism in response to aromatic hydrocarbons.