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We present phylogenetic analyses for four anaerobic bacterial isolates from samples collected in the Schirmacher Oasis and Lake Untersee in Antarctica. Near-full length of 16S rRNA genes were amplified from the four strains and sequenced for identification of their close relatives and their phylogenetic relationships. Strain A7P-90m shared a low 16S rRNA sequence identity of around 85% with its closest relatives within the Bacteroides phylum. This low level of sequence similarity suggests that it may represent a novel family within this phylum. The 16S rRNA sequence identity between strain LZ-22 and its closest relatives Granulicoccus phenolivorans and Propioniferax innocua within the Propionibacteriaceae family were 91.9% and 93.2%, respectively. This low level of sequence similarity suggests that it may represent a novel genus within this family. Strains 9G and ISLP-3 were closely related to known species of the genera Halolactibacillus and Sanguibacter, respectively. However, the 16S rRNA sequence identities between strains 9G and ISLP-3 and their close relatives were too high to make reliable taxonomic inferences (i.e., 99.9% between 9G and H. miurensis, and 98.6% between ISLP-3 and S. suaresii). Because the recA gene delivers higher resolution for taxonomic inferences than the 16S rRNA gene, the primers for conserved recA gene were designed for PCR amplification and sequencing from Halolactibacillus and Sanguibacter type strains. Strain 9G shared a recA sequence identity of 99.6% with its closest relative H. miurensis, suggesting that it is a subspecies. The recA sequence identity shared between strain ISLP-3 and its six closest relatives ranged from 85.9 similar to 90.2%. This result is consistent with this strain representing a novel species within the genus Sanguibacter. Based on the molecular study presented here and the phenotypic properties presented elsewhere, we propose that strain LZ-22 is a representative of a novel genus and species, with proposed names Raineyella antarctica gen. nov., sp. nov. Strain ISLP-3 is a representative of a novel species, Sanguibacter gelidistatuaria sp. nov. Strain A7p-90m may represent a novel family within the order Bacteroidales. Chemotaxonomic characterizations of these strains are underway to gather more evidence for the proposed classifications.