Characterisation of the indigenous bacteria involved in the ex-situ aerobic bioremediation of a polycyclic aromatic hydrocarbon-contamined soil

Polycyclic aromatic hydrocarbons (PAHs), mainly produced by petrogenicactivities and by the natural and anthropogenic pyrolysis of organicmatter, are chemicals of environmental concern, and, due to theirhydrophobicity, they are persistent in soils and sediments1-5. Their presence in contaminated soilsgenerally depends on the susceptibility of each PAH isomer to microbialdegradation and on some abiotic and environmental factors which caninfluence the process6. In-situ and ex-situmethods have been proposed to remediate PAH-contaminatedsoils7. In a previous work, we have shown that aPAH-contaminated silty-clay soil, referred to as S1, can be bioremediatedby stimulating its indigenous microflora in well-defined reactorsystems1,2. S1 PAHs with two, three, and four rings were found to disappear insequence, with depletion rates which decreased with the increase of thenumber of molecule rings and, among the compounds with the same number of rings, with the increase of the degree ofmolecule saturation and in the presence of a methyl group2. The increase in bacterial viable cell concentration and the largeCO2 production associated with the PAHs disappearance during the treatmentsuggested that S1 indigenous microorganisms were largely responsible forthe described PAH depletion2. Thus, the present study was undertaken in order to isolate andcharacterise the indigenous bacteria responsible of the PAH biodegradationin S1 soil.