controls 4-Nitroquinoline-N-oxide (4NQNO) and 2-amino fluorene (2AF), dimethyl sulfoxide (DMSO) was used as solvent; for methy-methane sulphonate (MMS) and sodium azide, water was used as a solvent. Positive controls for strains TA97a-4NQNO; TA100-MMS and TA1535-sodium azide, were used without metabolic bioactivation and 2AF for all the strains with metabolic bioactivation. After 48h incubation of agar plates at 37 °C counting of bacterial colonies was performed.