MPI-BGC Colloquium

Most bacteria are able to survive and thrive in environments with fluctuating nutritional conditions. Moreover, bacterial cells also interact with multiple stress factors that simultaneously occur in natural environments. The production of neutral lipids, such as wax esters (WE) and triacylglycerols (TAG), may be part of the complex strategic survival mechanisms evolved by some prokaryotes, which allow them to colonize and thrive in natural environments. These lipids are convenient storage compounds for carbon and energy, which can be utilized for cell survival in energy-poor environments. The potential application of such neutral lipid-producing microorganisms as a source of single cell oil useful for the production of biofuels or other derived industrial products, promoted further studies which contributed with our understanding of the process. Single cell oils are lipids extracted from microorganisms, which could serve as alternative oil sources for the production of biofuels with similar efficiency as petroleum diesel. Current research efforts are being focused on the biochemistry and genetics of oil-accumulating bacteria for designing a scalable and commercially viable oil-producing system from inexpensive feedstocks. In this context, the application of omic approaches as well as the functional identification and characterization of key genes/proteins from model bacteria, enabled significant advances in the fundamental knowledge on WE/TAG metabolism. Such global works clearly demostrated that the massive biosynthesis and accumulation of TAG by rhodococci demands a complex and specific metabolic network involving several reactions at different levels of the metabolism. The TAG biosynthetic machinery of oleaginous rhodococci includes enzymes involved in different reactions of metabolism, transporter proteins, structural components of lipid inclusions, and transcriptional regulators at different hierarchical levels (global and specific regulators). At this time, some genes from the oleaginous R. opacus PD630 and R. jostii RHA1 strains directly related to TAG metabolism have been cloned and functionally characterized in our laboratory. In this presentation, main aspects on the composition of the TAG-accumulating machinery necessary for supporting biosynthesis and accumulation of such lipids in rhodococci will be discussed, as well as some molecular strategies to improve TAG production.