Abstract: An accelerated micro-organism culture method is for decomposing harmful substances. For this purpose, the cultivation, mutagenic treatment and stabilization of the micro-organisms are carried out simultaneously in a mutation fermenter containing a nutrient-rich basic medium (basic medium 1); selection is carried out in a selection fermenter containing a basic medium which is low in nutrients and is enriched with the harmful substance (basic medium 2); small amounts of biomass released from the nutrient-rich basic medium (basic medium 1) of the mutation fermenter are continuously removed from the mutation fermenter and transferred to the selection fermenter. Small amounts of biomass released from the basic medium which is low in nutrients (basic medium 2) of the selection fermenter are removed from the selection fermenter and transferred to the mutation fermenter. The entire process is carried out continuously in alternating selection and mutation phases, in the manner of a repeated cycle.