Carboxysomes: The next frontier in biotechnology and sustainable solutions

Some bacteria possess microcompartments that function as protein-based organelles. Bacterial microcompartments (BMCs) sequester enzymes to optimize metabolic reactions. Several BMCs have been characterized to date, including carboxysomes and metabolosomes. Genomic analysis has identified novel BMCs and their loci, often including genes for signature enzymes critical to their function, but further characterization is needed to confirm their roles. Among the various BMCs, carboxysomes, which are found in cyanobacteria and some chemoautotrophic bacteria, and are most extensively investigated. These self-assembling polyhedral proteinaceous BMCs are essential for carbon fixation. Carboxysomes encapsulate the enzymes RuBisCo and carbonic anhydrase, which increase the carbon fixation rate in the cell and decrease the oxygenation rate by RuBisCo. The ability of carboxysomes to concentrate carbon dioxide in crops and industrially relevant microorganisms renders them attractive targets for carbon assimilation bioengineering. Thus, carboxysome characterization is the first step toward developing carboxysome-based applications. Therefore, this review comprehensively explores carboxysome morphology, physiology, and biochemistry. It also discusses recent advances in microscopy and complementary techniques for isolating and characterizing this versatile class of prokaryotic organelles.