Ecophysiological Characteristics of Psychrotolerant Actinomycetes in Tundra and Forest Landscapes

Abstract

Actinomycetic complexes of soils and plant substrates from tundra and taiga zones of Russia and Finland have been studied. A molecular cytogenetic technique—fluorescence in situ hybridization (FISH) method—has been applied to estimate the metabolically active component in the representatives of the Actinobacteria. In the prokaryotic microbial communities of studied plant substrates, the biomass of metabolically active psychrotolerant representatives of Actinobacteria was determined upon incubation at 5°C reached 34% of the total bacterial biomass; at the incubation temperature of 20°C, it increased to 56%. Under conditions of low temperature, psychrotolerant actinomycetes displayed active growth with the development of both substrate and aerial mycelium. The abundance of psychrotolerant actinomycetes reached thousands and tens of thousands CFU/g for taiga mosses in Finland and increased to millions CFU/g for tundra flowering plants in the Taimyr Peninsula of Russia. It decreased in the sequence: peat soil > plants > moss cushions > litter horizons. The length of actinomycetic mycelium in tundra plants varied from 98 m/g at 5°C to 291 m/g at 20°C; in taiga mosses, it varied from 120 to 180 m/g, respectively. The complex of psychrotolerant actinomycetes was mainly composed of colorless species of the Streptomyces genus possessing specific ecophysiological features, such as the change in the color of substrate and aerial mycelium, the appearance of pigmentation, and the increase in the growth rate upon higher incubation temperatures. More than 60% of actinomycetes isolated from taiga mosses of Finland were represented by psychrotolerant species of Micromonospora genus.