Impact of oil pollution on sediment bacterial diversity and enrichment of hydrocarbon-degrading bacterial communities from Ancona harbor

Several coastal sites are threatened in the Mediterranean Sea by the strong impact of the anthropogenic activities, contributing to the occurrence of a high risk for the healthiness of this unique marine ecosystem. The Adriatic Sea, a semi-enclosed basin in the Mediterranean Sea, hosts different vulnerable and contaminated environments, including the Ancona harbor which sediments have been investigated in the present study by cultivation dependent and independent approaches. The analysis of bacterial diversity by DNA-based fingerprinting unveiled a different composition of the microbiome dwelling contaminated and not contaminated sediments in the Ancona harbor. Several slurry microcosms were set up, using oil hydrocarbons as the sole carbon source, to enrich and identify hydrocarbon degrading bacterial consortia from the autochthonous microbiome of the polluted sediments. Denaturing Gradient Gel Electrophoresis (DGGE) applied on the 16S rRNA and alkB gene revealed that both the site of sediment collection and the supplemented pollutants are involved in the selection of peculiar bacterial communities. Although different bacterial genera were identified by DGGE analysis, the established bacteria collection included almost exclusively bacteria belonging to the specie Alcanivorax borkumensis. Overall, the results indicated the polluted sediments of the Ancona harbor as a promising habitat for the selection of valuable bacterial resources to be exploited for marine bioremediation. Furthermore, the results demonstrated the need of innovative cultivation approaches aimed to obtain in pure culture marine species that showed to be enriched by the presence of pollutants, but were not cultivated in standard laboratory conditions.