Carbon Metabolism in Lipid-Producing, Nitrogen-Starved Chlamydomonas reinhardtii

In recent years, studies have shown that lipid bodies produced by nitrogen-starved green algae such as Chlamydomonas reinhardtii may serve as viable alternatives of fossil fuels. While there is no doubt that these organisms are capable of producing energy-packed lipids, the exact pathway of how carbon is incorporated into the cells to make energy-storage molecules has yet to be determined. In order to determine this, the mutant strains sta6 and cw15 were grown using acetate as their main carbon source. Although both strains lack cell walls, sta6 lacks a key starch-producing enzyme. Because of this, it is known that sta6 primarily incorporates the exogenous acetate into triacylglycerides (TAGs) while cw15 primarily produces starch under nitrogen-starvation. The acetate was labeled with 1-13C acetate and tracked using nuclear magnetic resonance spectroscopy. It was found that the acetate is not incorporated into lipids and starch directly through typical metabolic pathways but through a bicarbonate system.