| Summary: | The microbial diversity in maritime meltwater pond sediments from Bratina Island, Ross Sea, Antarctica was investigated by 16S rDNA-dependent molecular phylogeny. Investigations of the vertical distribution, phylogenetic composition, and spatial variability of Bacteria and Archaea in the sediment were carried out. Results revealed the presence of a highly diverse bacterial population and a significantly depthrelated composition. Assessment of 173 partial 16S rDNA clones analyzed by amplified rDNA restriction analysis (ARDRA) using tetrameric restriction enzymes (HinP1I 5'GVCGC3'and Msp I. 5'CVGG3', BioLabs) revealed 153 different bacterial OTUs (operational taxonomic units). However, only seven archaeal OTUs were detected, indicating low archaeal diversity. Based on ARDRA results, 30 bacterial clones were selected for sequencing and the sequenced clones fell into seven major lineages of the domain Bacteria; the a, c, and d subdivisions of Proteobacteria, the Cytophaga–Flavobacterium– Bacteroides, the Spirochaetaceae, and the Actinobacteria. All of the archaeal clones sequenced belonged to the group Crenarchaeota and phylogenetic analysis revealed close relationships with members of the deep-branching Group 1 Marine Archaea.
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