Biodegradation of Crude Oil by Individual Strains and a Mixed Bacterial Consortium in Simulation of Marine Environment

Petroleum hydrocarbons are the most widespread contaminants in the marine environment. The fate of petroleum in sea water is largely controlled by mechanical, physical and chemical factors which influencing the natural transformation of petroleum (oil weathering) and oil bio-degradation. On the basis of these considerations, bioremediation techniques have been developed and improved for cleaning up oil-polluted marine environment as alternative to chemical and physical techniques. To elucidate the cooperative action of mixed microbial populations in the biodegradation of crude oil, we constructed artificial consortia composed of two to three bacteria (Alcanivorax borkumensis strain SK2, Rhodococcus erythropolis HS4 and Pseudomonas stutzeriSDM) capable to degrade oil hydrocarbons. Using these consortia, we investigated the mechanism by which efficient biodegradation of crude oil could be accomplished by the mixed populations for application in natural environment (bioaugmentation). All experiments were carried out in microcosms systems containing seawater (with and without inorganic nutrients) and oil was used as sole carbon source. All data obtained (Total DAPI Count, Live/Dead staining, Card-FISH and GC-FID hydrocarbons analysis) confirmed the fundamental role of bacteria belonging to Alcanivorax genus in degradation of linear hydrocarbons in oil polluted environments. Indeed, in all experimentations carried out in seawater with or without inorganic nutrients showed as rates of oil degradation are almost total in presence of this bacterium.