Relationship between β-oxidation pathway and the hydrocarbon-degrading profile in actinomycetes bacteria

Nine non-sporulating soil actinomycetes bacteria belonging to Rhodococcus, Nocardia, Gordonia and Dietzia genera were investigated for their hydrocarbon-degrading abilities. All strains showed similar hydrocarbon-utilizing profiles. Normal- and branched-alkanes, alkylbenzenes and alkylcycloalkanes were utilized as carbon sources more readily than monoaromatics, polyaromatics and cycloalkanes. Thus, the studied strains showed more affinity for a variety of hydrocarbons, which were channelled to β-oxidation pathway for degradation; such as pentadecane, hexadecane, 2,6,10,14-tetramethyl pentadecane (pristane), phenyldecane, gas–oil and kerosene. In addition, these hydrocarbons were utilized for the biosynthesis and accumulation of triacylglycerols by the studied bacteria during cultivation under nitrogen-limiting conditions. The results of this study showed that β-oxidation pathway, solely or tightly coupled to the de novo fatty acid biosynthesis route, serves as the main source of fatty acids for lipid biosynthesis during growth of the cells on hydrocarbons, which supported good growth of cells. The metabolism of non-sporulating actinomycetes may adapt to the utilization of hydrocarbons with an alkyl side chain in their structure for the production of a large variety of lipids with different complexity and functions. The degradation of hydrocarbons containing an alkyl side chain in their chemical structure, as well as the capability of actinomycetes for transforming such hydrocarbons in cellular lipids under conditions that occur often in the nature, make these microorganisms potential candidates for bioremediation activities in contaminated environments.