Dynamics of hydrocarbon-degrading bacteriocenosis of an experimental oil pollution in Patagonian soil

Changes of the bacteriocenosis in oil polluted Patagonian soil were studied during a bioremediation process performed in a controlled laboratory experiment. A selective enrichment of hydrocarbon-degrading bacteria was observed, from 0.028% at the beginning of the assay to almost 100% 2 months after spillage. During the experiment 45.48% of oil was degraded. Significant correlation between crude oil, aliphatic, aromatic and asphaltic fractions, and the bacteria able to utilize such hydrocarbons was observed. Both the asphaltenes fraction and asphaltene-degrading bacteria increased throughout the assay, suggesting a biological transformation of hydrocarbons in compounds of higher complexity. In addition, important variations in the physiological and taxonomic diversity of the bacteriocenosis were detected. After oil pollution, representative strains of the bacterial community exhibited the ability to metabolize a broad spectrum of hydrocarbons. During the first 5 months of the experiment a predominance of Gram negative bacteria was found and, subsequently, Gram positive microorganisms increased. Some of the isolated bacteria, such as members of Rhodococcus genus, displayed a wide potential for hydrocarbon biodegradation and persistence in the studied environment. These results indicate the importance of autochthonous bacteria for hydrocarbon-polluted soil bioremediation.