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COASTAL MARINE SEDIMENTS OF PATAGONIA REVEAL NEW TYPES OF DIOXYGENASES
JUAN PABLO RIVA MERCADAL; GUILLERMO DEL PRADO; NELDA OLIVERA; MARCELA FERRERO; HEBE DIONISI
Jornada; 11th Symposium on Microbial Ecology ISME-11; 2006
International Society for Microbial Ecology
Polycyclic aromatic hydrocarbons (PAHs) can be found in the marine environment as a result of anthropogenic activities or due to natural events such as petroleum seeps. The diversity of PAH-degrading microorganisms in this environment remains largely unknown. Primer sets targeting different types of initial PAH-dioxygenase genes were designed or selected from the literature in order to analyze the diversity of PAH-degrading populations in coastal sediments of Patagonia. Using a culture-independent approach, dioxygenase genes were amplified from total DNA isolated from surficial sediment samples, cloned and sequenced. These gene libraries indicated the presence of dioxygenase genes with similarities of more than 95% with phnAc-like genes from Alcaligenes faecalis AFK2 and Burkholderia sp. Ch1-1, Ch3-5, Cs1-4 and Eh1-1, all strains isolated from terrestrial environments. In addition, most samples contained dioxygenases closely related to phnA1-like genes cloned from marine PAH-degraders from the genera Cycloclasticus. Interestingly, some clones showed identities of only approximately 60-66% at the amino acid level with previously identified dioxygenase genes. These sequences carry bacterial ring hydroxylating dioxygenase alpha-subunit signatures, suggesting that they are actually novel types of dioxygenases. Using a culture-dependent approach, PAH-degrading bacteria were isolated from the sediments, and identified by 16S rDNA sequencing. Isolates were closely related to the genera Cobetia and Halomonas (98% identities) within the Family Halomonadaceae. Attempts to amplify PAH-dioxygenase genes from these isolates resulted unsuccessful so far. These results will be the foundation to understand the ecological significance and to evaluate potential biotechnological applications of these microbial populations.