Degradação de Óleo por Bactérias Isoladas dos Sedimentos de Manguezal da A.P.A. de Guapimirim - Baía de Guanabara - RJ - Brasil

Abstract

In the present work the in situ petroleum remediation in a mangrove ecosystem was evaluated, comparing the natural and stimulated degradation by hydrocarbonoclastic bacteria consortia (HBC) isolated from sediment samples. 9 microcosms experiments were installed in the Guapimirim Environmental Protection Area (Guanabara Bay): 3 experiments were control, 3 were contaminated only with petroleum (SP) and 3 were contaminated with petroleum and with the application of the HBCs isolated from this site (PB). The petroleum effect on microorganisms activity was evaluated by analysis of Electon Transport System Activity and the activity of exoenzymes esterases . The evaluation of oil biodegradation was done by the analysis of hydrocarbons (soxhlet microwaves extractions and chromatography gas spectrometry with mass detection). The population diversity of hydrocarbonoclastic communities (of microcosms SP and CBHs) was carried out by analysing the terminal restriction fragment lenght polimorphism (t-RFLP). The isolated hydrocarbonoclastic bacteria that grew on oil hydrocarbons (octadecane, pristane, naphthalene, fluoranthene e pyrene) as the only source of carbon and energy, were identified by gene sequencing of rDNA 16S. The oil degradation was only observed after 3 months from the oil treatment, suggesting a long lag fase for microorganism to adapt to the petroleum on the tested natural condictions. Eleven strains were isolated from HBCs and 53 from the microcosm sediment samples (SP). This is the first time that hydrocarbonoclastic strains have ever been isolated from Guanabara Bay, what shows the high potential of this environment for developing auto-recovery mechanisms. The phylogenetic characterization showed that, among the 64 strains, there were 25 different species (of 15 distinct genera). Some of them are recognized for their hydrocarbon degrading ability (e.g., Marinobacter sp. and Alcanivorax sp). Though, for some genera, it is the first time that this ability was observed (like Hydrothermal vent). In addition, for the strains that grew on polycyclic aromatic hydrocarbons the presence of dioxygenase gene was observed (sub-unity gamma and beta nahAc nahAd of a naphthalene-dioxigenase from Pseudomonas sp. 9816-4, U49496), undelining the degrading potential of such species and suggesting the presence of horizontal transfer among the isolated strains.