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Autochthonous bacteriocenoses in semiarid soils in Patagonia were found to be capable of rapidly adapting to high contamination with crude oil. This adaptation at community level is due to the selective enrichment of hydrocarbon-utilizing bacteria always present in these soils. Immediately after a heavy contamination with crude oil, the autochthonous bacteriocenosis contained about 28% hydrocarbon-utilizing bacteria which could be classified into eight ecotypes with characteristic metabolic profiles. Mainly n-alkanes were used as growth substrates of representative strains. After seven months' exposure to crude oil, the bacteriocenosis consisted almost entirely of hydrocarbon-utilizing bacteria. At least fourteen ecotypes were distinguishable, and the majority of representative strains were able to metabolize a broad spectrum of aliphatic and aromatic hydrocarbons. Corresponding to the significant alteration of the physiological diversity, drastic changes to the taxonomic diversity were also found. Whereas at the beginning of the study the autochthonous bacteriocenoses were dominated by GRm-positive genera of the Actinomycetales (Dietzia, Gordona, Nocardia, Rhoabcoccus, Streptomyces) with high ecological potency, after just two months' exposure to crude oil, GRAMnegative bacteria (especially Pseudomonas srurzeri) became predominant within the hydrocarbonutilizing bacteriocenoses accompanied by some GRAM-positive genera of the Actinomycetales with a significantly lower abundance. These findings underline the importance of Pseudomonas and some genera of Actinomycetales for processes of natural attenuation and the technically supported in situ bioremediation of soil polluted by crude oil in Patagonia.

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The electrokinetic technique is used to remediate hydrocarbon-contaminated soil. The aim of this paper is to evaluate the feasibility of using this technology to remediate oilcontaminated soils in the Gulf of San Jorge. The soils used in this experiment were unsaturated soils contaminated by oil field operations being carried out in the area and previously remediated by landfarming. A potential difference of 0.5V cm -1 was applied to the electroremediation cells for 120 days; bridges of phosphate salt were used for the cells. Total hydrocarbons decreased from 4.22% to 3%, modifying the percentages of aliphatic, aromatic and polar hydrocarbons. The pH changed from 7.96 to 8.6 and 7.1 in the cathode and anode, respectively. The final pH values were compatible with the degrading bacterial community, whose colony-forming numbers did not present any alteration. On the cathode, there was an increase in the percentage of Gram-positive bacteria. Most of the species isolated were identified as Microbacterium luteus.Keywords: electrokinectic, TPH, bacteria, unsaturated soil. IntroducciónLa electrorremediación es una tecnología utilizada para restaurar suelos contaminados por la aplicación de un campo eléctrico a partir de corriente directa [1]. Al aplicar corriente directa en un suelo, los contaminantes existentes pueden ser removidos debido a que se producen, en su matriz, movimientos de electromigración, electroósmosis y electroforesis [2]. Esto produce un aumento de la biodisponibilidad de compuestos orgánicos, lo que lleva a un aumento en la biodegradación de los mismos [3]. Existen diferentes factores que influyen en el proceso. Uno de ellos es el pH, se produce una acidificación en la región del ánodo y una alcalinización en la del cátodo. Otro factor es el contenido de agua