Abstract: The invention provides transgenic Escherichia coli cells comprising a mutation in cydAB gene, and/or cyoABCD gene, and/or cbdAB gene, and/or ygiN gene, wherein the mutation reduces (preferably, but not necessarily, by 100%) the cytochrome oxydase activity of a protein encoded by cydAB gene, and/or cyoABCD gene, and/or cbdAB gene, and/or ygiN gene. In a preferred embodiment, the mutation is a deletion of the cydAB gene, cyoABCD gene, and cbdAB gene. In another embodiment, the mutation is a deletion of the cydAB gene, cyoABCD gene, cbdAB gene, and ygiN gene.