| Summary: | A total of 253 hydrocarbon-oxidizing bacterial isolates were achieved from eight Antarctic surface seawater samples enriched on diesel oil at 4°C. Isolates were screened by ampliWed ribosomal DNA restriction analysis prior to 16S rRNA gene sequencing. Sequences were compared to those in available databases using the Basic Local Alignment Search Tool network service to determine their approximate phylogenetic aYliations. The majority of the isolates were aYliated to the Actinobacteria (75.9%) and the Gamma-Proteobacteria (22.9%). The Alpha- and Beta- Proteobacteria represented 0.8 and 0.4% of total isolates, respectively. The Actinobacteria were predominantly allocated to the genera Arthrobacter, Cryobacterium and Rhodococcus. The Gamma-Proteobacteria were mainly found to be related to the genus Pseudomonas. Conversely, the Alpha- and Beta-Proteobacterial isolates shared the highest degree of sequence identity with unclassiWed bacteria. DiVerences in the distribution of the detected phylotypes were observed among the analyzed samples. Isolates representing each phylotype were selected for further characterization, including phenotypic assays and screening for the growth ability in the presence of individual hydrocarburic substrates as the sole supplied carbon and energy source. Isolates possessed diVerent patterns of substrate utilization. Aliphatic hydrocarbons supported the growth of a higher number of isolates than aromatics. Results conWrm the ability of our Antarctic marine bacteria to utilize hydrocarbons at low temperature and therefore suggesting that isolates with diVerent substrate speciWcities can act in nature as a consortium in the utilization of complex hydrocarburic mixtures.
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