Capacités dégradatives de bactéries et de champignons isolés d'un sol contaminé par un fuel

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Abstract
The long-term influence of a fuel spill on the bacterial and fungal communities of an agricultural soil was studied. Three years after the contamination, biodegradation of the fuel in the soil was achieved and after 5 years the residual compounds had no significant effect on the density and the specific composition of the microbial populations of the soil. Hydrocarbon-oxidizing bacteria Corynebacterium and Nocardia spp. were isolated. Most of the active fungi were Aspergillus and Penicillium spp., but strains of Paecilomyces, Acremonium, Fusarium, and Gliocladium were also identified. In laboratory experiments, the biodegradation rate of a reference crude oil by pure cultures of oil-degrading strains was nearly the same as in mixed cultures. The biodegradation potential of the strains isolated from the control plot was as high as strains isolated from the oiled plot. In the soil, as in laboratory cultures, the saturate hydrocarbons were more degraded than the aromatics, whereas the resins and asphaltenes were resistant to microbial attack, as were polycyclic alkanes steranes and triterpanes. Nocardia degraded preferentially the aromatics and attacked significantly the asphaltenes, as did Fusarium oxysporum. Aspergillus niger, Aspergillus flavus, and Fusarium oxysporum degraded part of the resins. The spectrum of the initial degradation of petroleum by the most active fungi and bacteria was identical, and it appears that the enzymatic equipment necessary to oxidize hydrocarbons is quite complete in these strains.