Prélèvement, stockage intracellulaire et dégradation des hydrocarbures polycycliques aromatiques par un champignon tellurique : Fusarium solani

Abstract

Polycyclic aromatic hydrocarbons (PAHs) are of great environmental concern due to their mutagenic and carcinogenic properties. Their persistence in ecosystems is due to their low water solubility which results in their binding to particulates in soils, sediments and atmosphere. Bioremediation represents the major route for the ecological recovery of PAHs contaminated sites. The aim of this work was to investigate the uptake and storage of benzo[a]pyrene by a non white-rot fungus, Fusarium solani, and to characterize, by cytological methods, the intracellular fluorescent vesicles observed when growing the fungus on synthetic medium in presence of benzo[a]pyrene. We have demonstrated that PAHs uptake into fungal hyphae was a passive phenomenon. Indeed, benzo[a]pyrene uptake and storage in Fusarium solani was not prevented at 4°C or in the presence of cytochrome oxidase inhibitor (sodium azide). The use of two cytoskeleton modulating drugs (colchicin or cytochalasin) suggested that microtubules and actine filaments were not involved in PAHs transport. Ultrastructural study showed that PAHs incorporation was not associated with specific structures. The use of Sudan III and Rhodamine B stainings showed that PAHs were accumulated in pre-existing structures corresponding to lipid vesicles. We found that Fusarium solani, was able to store into lipid vesicles and degrade efficiently a large scale of PAHs. The degradation rates were about 84, 70, 58, 34 and 40% for anthracene, pyrene, benzo[a]pyrene, benzo[ghi]perylene and coronene respectively. We also showed that the PAHs intracellular storage was not restricted to the Deuteromycotina fungus Fusarium solani, but could be generalized to numerous other fungi, even poor degraders, belonging to different genera.