干旱区生态环境知识资源中心

The population density, size, and biomass of the soil bacteria from a mountain meadow-steppe soil of Tajikistan and a light sierozem of the Negev Desert have been analyzed using the method of "cascade" filtration. It was shown that, when cultivating small fractions of soil bacteria, the total number of bacteria increased by 1.5 times and the bacterial size became greater. The number of coarse cells with a size of 1.85 and 0.43 mu m essentially increased in both soils. If the contribution of these fractions was about 10-20% in the initial soils, it increased up to 50-60% in the incubated filtrates. The cells with a size of 0.38 and 0.23 mu m accounted for about 70% of the total bacteria in the initial soils, while, in the incubated filtrates, the share of 0.23 mu m cells composed about 30% in the filtrate and that of 0.38 mu m cells reached 45-50% in the filtrate. The average diameter of the bacteria increased from 0.4 to 0.8-0.9 mu m; the biomass of bacteria in these filtrates increased by 7-8 times in comparison with the initial soils at the expense of an increasing number of large cells after cultivation.