Respuesta de comunidades bacterianas a la adición de hidrocarburos en sedimentos costeros de la Patagonia

KUIN, RUUD; DIONISI, HEBE; LOZADA, MARIANA

Puerto Madryn

Jornada; IV Jornada de Becarios CENPAT-CONICET; 2014

Espacio Becarios CENPAT-CONICET

This research focused on the capabilities of bacterial communities from the marine environment to respond to hydrocarbon exposure, especially Polycyclic Aromatic Hydrocarbons (PAHs), by means of the selection of specific populations associated with their biodegradation. Coastal intertidal sediments from three sites with different environmental characteristics and hydrocarbon exposure history were chosen (Playa Fracasso, nonpolluted, Chubut; Caleta Córdova, polluted, Chubut; Bahía Ushuaia, polluted, Tierra del Fuego). For each, an experimental setting of sediment-seawater slurries was built, with four conditions: no external hydrocarbon addition, oil (0,4% v/v), phenanthrene (0.2% w/v), and pyrene addition (0.2% w/v). After 20 days of incubation at 15°C, total DNA  was extracted and analysed by quantitative real-time PCR (qPCR) of genes coding for aromatic-ring-hydroxylating dioxygenase (ARHD). This enzyme catalyzes the first step of PAHs metabolic pathway in bacteria. Three ARHD genes were tested: phnA1 (described in Cycloclasticus spp., obligate oil-degrading marine bacteria), and two novel variants from yet-uncultured microorganisms, described for the first time at these sites (D and T variants). The effect of hydrocarbon addition in the amount of ARHD copies in the extracted DNA was evaluated in each case. In general, dioxygenase genes increased their abundances after hydrocarbon addition, however the response in the sediments from the non-polluted site was weaker. The strongest response was observed for the phnA1 gene, reaching more than 107 copies per microgram of DNA in some conditions. T variant was found in high abundance and also showed a response to PAHs in both polluted sites, while D variant showed a response only in sediments from the subantarctic site. Our findings allowed us to identify key bacterial populations associated with PAH biodegradation in coastal sediments of Patagonia, and showed that both the type of environment and the hydrocarbon exposure history can influence the selection of specific  populations at each site.