The newest microbiological research of soils and plants was described in the paper. Physical and other methods were used in observations of soils and plants. The relation between biological activity and soil fertility was examined. The research on the role of the microorganisms in detoxication of soils was described as well as distribution of microorganisms in soil - depending on granulometric particles and soil aggregates. Attention was paid to the influence of soil bulk density and humidity on soil microorganisms. Special attention was paid to the influence of organic matter on microorganisms and soil properties.