Abstract: | An analysis of the abundance and taxonomical structure of the heterotrophic block of aerobic and conditionally anaerobic bacteria in hydromorphic tundra and taiga soils was carried out. The decline of the cultivating temperature from 20° to 5° did not result in the reduction of bacterial abundance. The spectrum of the bacterial dominants in the northern cryogenic soils is wider under 4–6°, which is indicative of the lowtemperature adaptation of bacteria. Oligotrophs and copiotrophs predominate the bacterial communities of the explored soils. However, among hydrolytic bacteria, active chitin destructors, represented by Bacillus and Janthinobacterium, were found. |