Bacterial communities in the soils of cryptogamic barrens of East Antarctica (the Larsemann Hills and Thala Hills oases)

Bacterial communities from the soils of cryptogamic barrens in the Thala Hills and Larsemann Hills oases of East Antarctica were examined. The total number of bacteria in the studied soils was no higher than 108 cells per gram of soil, which is an order of magnitude lower than the values typically found in the soils of temperate regions. The portion of viable cells reached 60% and more, which attests to the high tolerance of the bacteria to the impact of adverse environmental factors. The maximum values of the total number and viability of the bacteria were found in the fine earth material immediately under the stony pavement. For the first time, the high content of the filterable forms of bacteria (FFB) was found. In some of the samples, their portion reaches 70-80% of the total number of bacterial cells. Data on the high numbers and viability of the bacterial cells and on the phylogenetic and morphological diversity of FFB allow us to attribute the latter to the pool of bacterial cells ensuring their preservation under unfavorable environmental conditions. The concentrations and total pools of bacterial biomass in the studied soils are much lower than those in the zonal soils of temperate regions. Bacterial communities in the studied soils combine the high tolerance toward the adverse environmental factors (as seen from the high portion of viable cells, the formation of the nanoforms of bacteria, and the participation of bacteria in the subaerial biofilms) with the low total number and biomass of the bacterial cells.