EN
Additive pollution in a form of soil salinity due to NaCl and lead-free petrol changed the number of microorganisms taking an active part in nitrogen conversions. Nitrifying then proteolytic bacteria appeared to be the most sensitive; the least changes were observed in number of Azotobacter genus bacteria. Significant differences resulting from pollution between studied soil types occurred only in a case of protein-decomposing microorganisms: they were less in loamy soil than sand. There is an opportunity to direct the metabolic courses towards decomposing simpler organic compounds in a form of protein and lead-free petrol at the same time, which was confirmed on a base of microorganism number increase along with the increase of the product concentration in the soil as compared to the control.