The α-subunit of the polycyclic aromatic hydrocarbon ring-hydroxylating dioxygenases (PAH-RHD α) coding genes from Gram-positive and Gram-negative bacteria were characterized in diesel oil-contaminated and pristine soils from King George Island in Maritime Antarctica. PCR, cloning and sequencing methodologies were used, and nucleotide and deduced amino acids sequences were further analyzed using Basic Local Alignment Search Tool (BLAST), Clusters of Orthologous Groups of proteins (COG) and Kyoto Encyclopedia of Genes and Genomes (KEGG) tools. Few PAH-RHD α sequences sharing high identities with NagAc from Ralstonia sp. U2 and with NahAc from Comamonas testosteroni strain H were found in pristine soil. In addition, PAH-RHD α sharing 44-100% identity with dioxygenases described within the Gram-negative Pseudomonas, Polaromonas, Sphingomonas, Acidovorax and Burkholderia genera and Gram-positive Mycobacterium, Gordonia, Terrabacter, Nocardioides and Bacillus genera were found in contaminated soils adjacent to the Brazilian Antarctic Station Comandante Ferraz. To our knowledge, the presence of PAH-RHD α coding genes from Gram-positive PAH-degrading bacteria has never been evidenced in Antarctic soils. Beta-diversity comparison analysis showed a different distribution of Gram-negative PAH-degrading bacteria among the Antarctic contaminated sites. This study provides important information about the PAH bioremediation potential of the Antarctic soils studied here. © 2011 Elsevier B.V.