ALBERT

Description: Microorganisms can be found in very different cold soil environments playing a major role in nutrient cycling in these habitats. We studied the dominant bacterial composition from nine soil profiles located on Livingston Island, Antarctica. Two vegetated sites (moss-covered) and seven mineral soil sites were analysed. Total carbon (TC) and total nitrogen (TN) values were up to 26.50 % and 0.84%, respectively, for vegetated soils decreasing with depth whereas values for mineral soils were 〈0.50% and 〈0.10%, respectively. Soil pH was more acidic for vegetated and neutral to alkaline for mineral soils. Conductivity was low at all sites. Numbers of culturable heterotrophic bacteria were higher at vegetated sites. Nonetheless, significant numbers of culturable heterotrophs (102-105 cells g-1 dry weight) were found even in carbon depleted soils. DGGE fingerprints revealed a highly heterogeneous picture throughout the soil profiles. Subsequent sequencing of DGGE bands revealed in total 183 sequences that were affiliated to Acidobacteria, Actinobacteria, Bacteroidetes/Chlorobi, Chloroflexi, Cyanobacteria, Firmicutes, Gemmatimonadetes, Nitrospirae, Planctomycetes, Proteobacteria, and candidate divisions OD1 and TM7. Sequences could be assigned to altogether 87 OTUs, with a dominance of Bacteroidetes and Acidobacteria. PLFA analysis showed a lack in unsaturated fatty acids for most samples. Samples with prevalence of unsaturated over saturated fatty acids were restricted to several surface samples. It can be concluded that the presence of plants had an influence on the bacterial community composition by providing organic nutrients. Nevertheless, also bare maritime Antarctic mineral soils showed a diverse microbial composition with species so far untraced in other habitats.