Yarrowia lipolytica is able to metabolize high Mr hydrophobic natural compounds such as fatty acids and hydrocarbons. Characteristically, strains of Y. lipolytica can grow as populations with variable proportions of yeast and filamentous forms. In the present study, we describe the dimorphic characteristics of a variant designated as Y. lipolytica var. indica isolated from petroleum contaminated sea water and the effect of cell morphology on hydrocarbon metabolism. The variant behaved as a yeast monomorphic strain, under conditions at which terrestrial Y. lipolytica strain W29 and its derived strains, grow as almost uniform populations of mycelial cells. Using organic nitrogen sources and N-acetylglucosamine as carbon source, var. indica was able to form mycelial cells, the proportion of which increased when incubated under semi-anaerobic conditions. The cell surface characteristics of var. indica and W29 were found to be different with respect to contact angle and percent hydrophobicity. For instance, percent hydrophobicity of var. indica was 89.93 ± 1.95 while that of W29 was 70.78 ± 1.1. Furthermore, while all tested strains metabolize hydrocarbons, only var. indica was able to use it as a carbon source. Yeast cells of var. indica metabolized hexadecane with higher efficiency than the mycelial form, whereas the mycelial form of the terrestrial strain metabolized the hydrocarbon more efficiently, as occurred with the mycelial monomorphic mutant AC11, compared to the yeast monomorphic mutant AC1.

Crude oil is a complex mixture of hydrocarbons, basically composed of aliphatic, aromatic and asphaltene fractions along with nitrogen, sulfur and oxygen containing compounds. Major causes of oil contaminated soils include: leakage of storage tanks and pipelines, land disposal of petroleum wastes and accidental spills. Apart from damaging crops and affecting the fertility of soil, crude oil on the fi elds also affects livestock. The loss of soil fertility and toxicity of petroleum hydrocarbon at higher concentrations have been linked to displacement of nutrients and nutrient linkage, reduction in phosphorus and nitrogen availability, and anoxic conditions. Moreover, it can cause microbial community structure changes and a decrease in microbial diversity. The aromatics in crude oils such as a -pinene, limonene, camphene, and isobornyl acetate were observed to be inhibitory to the microorganisms. In recent years, there has been increasing interest in developing on site and in situ techniques for remediation of oil-contaminated soils. Bioremediation can be achieved by natural attenuation, biopiling, bioaugmentation, phytoremediation or rhizoremediation, singly or in combination. Numerous genera of bacteria are known as good hydrocarbon degraders. Most of them belong to Aeromonas, Alcaligenes, Acinetobacter, Arthobacter, Bacillus, Brevibacterium, Mycobacterium, Pseudomonas, Rhodococcus, Sphingomonas,