Many artificial organelles or subcellular compartments have been developed to tune gene expression, regulate metabolic pathways, or endow new cell functions. Most of these organelles or compartments were built using proteins or nucleic acids as building blocks. In this study, we demonstrated that capsular polysaccharide (CPS) retained inside bacteria cytosol assembled into mechanically stable CPS compartments. The CPS compartments were able to accommodate and release protein molecules but not lipids or nucleic acids. Intriguingly, we found that the CPS compartment size responds to osmotic stress and this compartment improves cell survival under high osmotic pressures, which was similar to the vacuole functionalities. By fine-tuning the synthesis and degradation of CPS with osmotic stress-responsive promoters, we achieved dynamic regulation of the size of CPS compartments and the host cells in response to external osmotic stress. Our results shed new light on developing prokaryotic artificial organelles with carbohydrate macromolecules.
Keywords: artificial organelles; compartment; polysaccharides; synthetic biology.