Growth of indigenous microorganisms in samples of crude oil in the absence of external electron acceptors

The diversity of a crude oil sample from the Tarragona basin (NE Spain) was assessed in order to determine the occurrence of potential hydrocarbon degraders able to grow in the absence of external electron acceptors. The experiments have been performed using an anaerobic bench-scale biofilm reactor. The taxonomic composition of the biofilm developed was determined at the end of the experiment (24 days) by DGGE analysis, and by sequencing of a bacterial 16S rRNA clone library. Amplification with archaeal primers was not detected. DGGE analysis of amplification products obtained using bacterial and eukaryotic primers yielded only one intense band in each case. Partial sequencing of each band revealed that the closest match corresponded to Bacillus sp. AJ519635 (99,8% similarity) and Saccharomyces kunashirensis AY046235 (100% similarity). On the other hand, the bacterial clone library confirmed the presence of Bacillus sp. in the biofilm. The bacterium has been isolated in pure culture and the identity of the isolate has been confirmed as the organism mentioned above. © 2004 Taylor & Francis Group, LLC.