Dissolved Inorganic Carbon-Accumulating Complexes from Autotrophic Bacteria from Extreme Environments

Area of Science:

• Microbiology
• Biochemistry
• Molecular Biology

Background:

• Autotrophic organisms utilize mechanisms to concentrate dissolved inorganic carbon (DIC) for CO2 fixation, especially in low-carbon environments.
• While studied in Cyanobacteria, DIC concentrating mechanisms in other bacterial and archaeal phyla are less understood.
• Novel multisubunit membrane-spanning complexes have been identified, with homologs distributed across 17 phyla of Bacteria and Archaea.

Purpose of the Study:

• To investigate whether DIC accumulation is a conserved function across diverse multisubunit complexes found in Bacteria and Archaea.
• To characterize the subunit requirements and substrate specificity of these novel DIC-accumulating complexes.
• To assess the potential for heterologous expression and application of these complexes in engineered systems.

Main Methods:

• Seven representative multisubunit complexes from diverse phyla and subunit configurations were selected for study.
• Heterologous expression of these complexes was performed in a high-CO2-requiring, carbonic anhydrase-deficient Escherichia coli strain.
• Growth rescue under low-CO2 conditions, intracellular DIC measurements, isotopic disequilibrium experiments, and ionophore treatments were employed for characterization.

Main Results:

• All seven expressed complexes rescued the low-CO2 growth defect of the E. coli host.
• Six of the seven complexes demonstrably elevated intracellular DIC concentrations.
• Two- and three-subunit complexes required all subunits for function, utilized CO2 as a substrate, and appeared to couple proton potential to DIC accumulation.

Conclusions:

• DIC accumulation is a conserved trait among diverse multisubunit complexes from various bacterial and archaeal phyla.
• These complexes exhibit functional conservation across different organisms and habitats, suggesting a universal role in carbon acquisition.
• Successful heterologous expression in E. coli highlights their potential for engineering applications in CO2 utilization and biomass synthesis.