Characterization of brackish anaerobic bacteria involved in hydrocarbon degradation: A combination of molecular and culture-based approaches

Abstract

Anaerobic bacterial communities were selected by successive enrichments, under light conditions, on selected hydrocarbon molecules (aliphatic and aromatic). The original inocula came from an oil-contaminated microbial mat developing in a refinery waste water treatment plant in Berre Lagoon (Mediterranean Sea, France). Bacterial communities able to degrade octadecane, naphthalene and fluoranthene were obtained. By using molecular methods (T-RFLP, ARDRA and sequencing), the composition of these bacterial communities were determined in order to identify the organisins involved in hydrocarbon degradation. Different functional groups, including denitrifiers, sulfate-reducers, anoxygenic phototrophs and fermentative bacteria could be identified. Molecular techniques permitted identification of the different functional groups and were therefore useful in the isolation of the key organisms involved in hydrocarbon degradation. Not all of these populations were able to utilize hydrocarbons as carbon source and/or electron donor. Indeed, among the different pure strains recovered from such enrichment cultures, some actively degraded hydrocarbon molecules (denitrifiers) whereas others have an indirect role (synergism, surfactant production). For example, several anoxygenic phototrophs have been isolated in pure culture and none use hydrocarbons for growth. Nevertheless, in addition to sulphide reoxidation originating from sulfate reduction, these microorganisms may play an important role in surfactant production.

Key words:

• Hydrocarbon degradation
• brackish lagoon
• anaerobic bacteria
• T-RFLP
• ARDRA