Saturday, 15 July 2006

Degradation of Naphthalene-Benzene-Ul-14c in Microbial- Inocculated Soils from Keller Peninsula, Antarctica.

Miriam A. Albuquerque1, Carlos E.G.R. Schaefer2, Victor V. Pereira2, and Bruno M.G. Alves3. (1) Centro Universitário Caratinga, Av Moacir de Mattos 49, Caratinga, 35300-047, Brazil, (2) Departamento do Solos-Universidade Federal de Viçosa, Campus da Universidade, Viçosa, Brazil, (3) UNEC, Av Moacir de Mattos 49, Caratinga, 35300-047, Brazil

An enrichment culture developed in a liquid media containing diesel oil as a carbon source was obtained from a cryosol sample collected in the diesel-affetced area near the Brazilian Station Comandante Ferraz, at Keller Peninsula, Antarctica. This mixed microbial culture demonstrated ability to degrade Naphthalene-benzene-14C in liquid growth media. An inocculum from the enrichment culture (50 ěl) was added to 15 g of two different soils samples collected from Keller Peninsula, Antarctica, determining the capability of this culture to enhance the degradation of naphthalene-benzene-14C added. One cryosol was collected from the same area from where the enrichment culture was obtained, whereas a second soil was collected from an acid-sulphide affected area nearby.These are the most common cryosols in Keller peninsula. Naphathalene-benzene-UL-14C (Sigma, 31.3 mCi/ mmol) was added to 15 g of soil with 25 ěl of diesel at a radioactivity concentration of 6.8 x 10-3 ěCi . g-1 of soil. Each treatment had 3 replicates. The 14CO2 evolved from the soils trapped to NaOH 0.5M solution was analysed using a Liquid Scintillation Counter (Beckman Instruments) during 18 days of incubation. After 10 days of incubation, about 20% of the naphthalene-benzene-14C added was degraded to 14CO2 evolved from the diesel area soil without added inocculum, while the same soil with inocculum presented a significantly increased degradation, reaching 55% of naphthalene-benzene-14C degraded to 14CO2 after 10 days of incubation. Contrasting, the acid, sulphide-affected cryosolos had only 5% of degradation of naphthalene-benzene-14C after 10 days of incubation. Also, the addition of inocculum to this acid cryosol did not promote significant increasing degradation of naphthalene-benzene-14C. Results showed that the microorganisms isolated from the diesel-contaminated cryosol are not well adapted to the acid conditions of the sulphide-affected soil.

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