Moniliella spathulata, an oil-degrading yeast, which promotes growth of barley in oil-polluted soil

The yeast strain Moniliella spathulata SBUG-Y 2180 was isolated from oil-contaminated soil at the Tengiz oil field in the Atyrau region of Kazakhstan on the basis of its unique ability to use crude oil and its components as the sole carbon and energy source. This yeast used a large number of hydrocarbons as substrates (more than 150), including n-alkanes with chain lengths ranging from C10 to C32, monomethyl- and monoethyl-substituted alkanes (C9-C23), and n-alkylcyclo alkanes with alkyl chain lengths from 3 to 24 carbon atoms as well as substituted monoaromatic and diaromatic hydrocarbons. Metabolism of this huge range of hydrocarbon substrates produced a very large number of aliphatic, alicyclic, and aromatic acids. Fifty-one of these were identified by GC/MS analyses. This is the first report of the degradation and formation of such a large number of compounds by a yeast. Inoculation of barley seeds with M. spathulata SBUG-Y 2180 had a positive effect on shoot and root development of plants grown in oil-contaminated sand, pointing toward potential applications of the yeast in bioremediation of polluted soils. KEY POINTS: • Moniliella spathulata an oil-degrading yeast • Increase of the growth of barley.

From oil spills to barley growth - oil-degrading soil bacteria and their promoting effects

Heavy contamination of soils by crude oil is omnipresent in areas of oil recovery and exploitation. Bioremediation by indigenous plants in cooperation with hydrocarbon degrading microorganisms is an economically and ecologically feasible means to reclaim contaminated soils. To study the effects of indigenous soil bacteria capable of utilizing oil hydrocarbons on biomass production of plants growing in oil-contaminated soils eight bacterial strains were isolated from contaminated soils in Kazakhstan and characterized for their abilities to degrade oil components. Four of them, identified as species of Gordonia and Rhodococcus turned out to be effective degraders. They produced a variety of organic acids from oil components, of which 59 were identified and 7 of them are hitherto unknown acidic oil metabolites. One of them, Rhodococcus erythropolis SBUG 2054, utilized more than 140 oil components. Inoculating barley seeds together with different combinations of these bacterial strains restored normal growth of the plants on contaminated soils, demonstrating the power of this approach for bioremediation. Furthermore, we suggest that the plant promoting effect of these bacteria is not only due to the elimination of toxic oil hydrocarbons but possibly also to the accumulation of a variety of organic acids which modulate the barley's rhizosphere environment.