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The main aim of our work was to evaluate the effect that the soil contamination with zinc, copper and cadmium has on the number of (CFU)Azotobacter, organotrophic bacteria and Streptomyces. The results of the experiment revealed their role in the CFU modification and the impact on the level of soil contamination with heavy metals. Organotrophic bacteria have a similar tolerance to the heavy metals as Streptomyces, since the lowest resistance characterizes the Azotobacter. The toxicity of the examined heavy metals can be ranked as follows (from the most sensitive to the least): Azotobacter>organotrophic bacteria>Streptomyces. It can be concluded that the succession of the microorganuisms is determined by the soil fertility, which stimulates both the characteristics and biochemical transformations, that occur in it through the mechanisms involved in reducing the negative impact of the heavy metals on the number of microorganisms.