Physiology, biochemistry and molecular biology of triacylglycerol accumulation by Rhodococcus

Abstract

Members of Rhodococcus genus are specialists in the accumulation of triacylglycerols (TAGs). Some of them can be considered oleaginous microorganisms since they are able to produce significant amounts of those lipids under certain conditions. In this context, R. opacus strain PD630 has become a model among prokaryotes in this research area. The basic knowledge generated for rhodococci could be also extrapolated to other related microorganisms with clinical importance, such as mycobacteria. The biosynthesis and accumulation of TAGs by Rhodococcus members and other actinomycetes seems to be a process linked to the stationary growth phase or as a response to stress. The chemical structure of rhodococcal TAGs can be controlled by the composition of the carbon source used. The biosynthesis and accumulation of novel TAGs containing unusual components, such as aromatic and isoprenoid fatty acids, by members of Rhodococcus and related genera have been reported. The low specificity of wax ester synthase/ diacylglycerol acyltransferase (WS/DGAT) enzymes, which catalyze TAG biosynthesis in prokaryotes, may contribute to the high variability of TAG composition. The occurrence of genes coding for WS/DGAT enzymes is highly redundant in rhodococcal genomes. The enrichment of genes and enzymes involved in TAG metabolism in rhodococci suggests the important role of these lipids in the physiology of these microorganisms. This article aims to summarize the most relevant achievements of basic research in this field, including the most recent knowledge that has emerged from studies on TAG accumulation by rhodococci and some unpublished results.