Diagnostic systems and method for determining the presence of a genotoxic and/or toxic compound in a sample

A diagnostic system comprising:

• a first transformed micro-organism capable of an increased reporter activity upon exposure to an environmental insult, said micro-organism having a stress inducible promoter sequence being operatively linked to a nucleic acid sequence encoding a reporter molecule resulting in a signal that can be assayed, and
• a second transformed micro-organism having a constitutive and non-stress inducible promoter sequence being operatively linked to a nucleic acid sequence encoding a reporter molecule resulting in a signal that can be assayed,
• wherein said second and first microorganisms are Salmonella typhimurium microorganisms selected from the group consisting of Ames test micro-organism, micro-organism designated by deposit number LMG P-18318, transformed TA98, transformed TA100, transformed TA102, transformed TA104, transformed TA1538, transformed TA7001 to transformed TA7005, and transformed TA7041 to transformed TA7046, said micro-organisms being suitable to cooperatively detect said environmental insult while eliminating false positive and false negative result.