Deuterium-depleted water modulates lipid metabolism in the freshwater microalga Chlorella sp

Extensive research has elucidated the biological effects of deuterium-depleted water (DDW) on animal cells, especially tumor cells, as well as the underlying molecular and cellular pathways. However, the biological effects of DDW on microalgae remain poorly understood. In this study, two DDWs with deuterium concentrations of 105 ppm and 25 ppm were used as culture media for Chlorella sp. Integrated metabolomic and lipidomic analyses were conducted to analyze the effects of deuterium depletion on its metabolic profile. Results revealed the pronounced effects of DDW on photosynthetic performance and metabolic activity. Notably, 105 ppm DDW markedly improved photosynthetic efficiency. However, algal biomass accumulation was not significantly enhanced by either DDW concentration during the 8-day cultivation period. Furthermore, DDW treatment upregulated amino acid and lipid metabolism pathways in Chlorella sp., particularly tyrosine metabolism pathway. Lipidomic profiling revealed a hierarchical sensitivity of lipid classes to DDW, following the order: glycerophospholipids (GP) > sphingolipids (SP) > glycolipids (GL) > fatty acyls (FA). Consistent with this, the biosynthesis of key structural lipids essential for biological membranes (i.e., GP and SP) increased significantly, whereas the biosynthesis of linoleic acid and α-linolenic acid decreased. Deuterium content served as a critical regulatory factor governing central metabolic processes in Chlorella sp. The results of this study offer valuable insights into the effects of deuterium depletion on microalgal physiology, metabolism, and population dynamics.