摘要: The nature of biological adaptation to deuterium oxide on an example cells various taxonomic groups prokaryotic and eucaryotic microorganisms realizing methylotrophic, chemoheterotrophic, photo-organotrophic, photosynthetic ways assimilation carbon substrates was discussed. It demonstrated that the effects observed at 2 H O, possess a complex multifactorial character connected cytological, morphological physiological changes – magnitude lag- period, time cellular generation, output biomass, parity ratio synthesized amino acids, proteins, carbohydrates lipids, also with evolutionary level organization investigated object pathways as well. These data suggest is phenomenon, affecting many systems, biosynthesis macromolecules, metabolism transport. Key words: deuterium, oxide, adaptation, isotopic effects, bacteria, micro algae.