Potential of hexadecane-utilizing soil-microorganisms for growth on hexadecanol, hexadecanal and hexadecanoic acid as sole sources of carbon and energy

Bacteria and fungi in pristine and oily desert soil samples were counted on inorganic medium aliquots containing 0.5% hexadecane, hexadecanol, hexadecanal or hexadecanoic acid, as sole sources of carbon and energy. It was found that the carbon and energy source most commonly utilized by soil bacteria was the alkane n-hexadecane, and by soil fungi hexadecanoic acid. Representative microorganisms were isolated and identified. The most predominant bacteria in all soil samples belonged to the genera Micrococcus and Pseudomonas; less dominant bacteria belonged to the group of nocardioforms. The most frequent fungal genera were Aspergillus and Penicillium, while Microsporium and Ulocladium were minor fungi. Irrespective of the substrate on which the microbial strains had initially been isolated, the majority of the isolated microorganisms could grow, albeit to a varying degree, on an inorganic medium containing any of the remaining three substrates as sole carbon and energy sources. Bacterial strains preferred the alkane as a carbon and energy source over any of its oxidation products, while fungal strains preferred to grow mainly on the fatty acids. Quantitative analysis by gas liquid chromatography revealed that the predominant bacterial and fungal isolates had a potential for the attenuation of the alkane and its immediate oxidation products in the medium. In view of the continuous release of hydrocarbon oxidation products by oil-utilizing microorganisms in oily environments, it is interesting that the indigenous microflora contribute to the uptake and utilization of all such intermediate compounds, thus, having a potential for efficient self-cleaning and bioremediation of oily soils.