Enrichment procedures for the isolation of xenobiotic-degrading bacterial and fungal strain: a focus on microbial ecology

LIFE-BIOREST (www.lifebiorest.com) is a EU-project aimed at the remediation of a soil polluted by PHAs, BTEX and alkanes through the application of selected consortia of fungi and bacteria. In the first phase of the project, we have isolated from the polluted soil about 220 fungal and 140 bacterial strains with degrading abilities. Most of the fungal strains belonged to Ascomycetes (mainly Aspergillus, Cladosporium, Fusarium and Scedosporium genera) even though about 20 Basidiomycetes were also isolated. Regarding bacteria, the most abundant genus was Pseudomonas followed by Achromobacter, Stenotrophomonas and Ochrobactrum. The isolates were obtained by means of a liquid enrichment approach on target contami- nants (naphthalene, pyrene, phenanthrene, benzene, alkanes and oil extracted from the soil): the enrichment lasted 3 weeks, and sub-culturing was carried out once a week. Since the pollution in the test soil involved several meters of depth, enrichments were carried out sep- arately using as inoculum homogenized soil samples from the 0-1, the 1-2 and 2-3 m depth. A total of 18 enrichment consortia were produced (6 target contaminants X 3 soil depths) for bacteria and other 18 for fungi, and sampled at day 0, 7, 14 and 21, giving a total of 144 samples. For each of these samples, DNA was extracted, amplified respectively for bacterial (16S) and fungal (ITS) biomarkers, and the resulting amplicons sequenced in Illumina. Results will be presented with the aim of assessing the ecological evolution of the microbial communities (bacteria and fungi) during the selective enrichment procedure in presence of different pollutants.