The variability in carbon fixation characteristics of several typical chemoautotrophic bacteria at low and high concentrations of CO₂ and its mechanism

The variability in carbon fixation efficiencies of four chemoautotrophic bacteria, namely, Alcaligenes hydrogenophilus DSM 2625, Pelomonas saccharophila DSM 654, Thiobacillus thioparus DSM 505 and Starkeya novella DSM 506, at 0.5% and 10% CO₂ concentrations was studied. The mechanism was clarified by analyzing the transcription characteristics of cbb gene. At 0.5% CO₂, DSM 654 showed higher carbon fixation efficiency but a lower cbb gene transcription level comparing with the other strains, which suggested that its ribulose-1,5-bisphosphate carboxylase/oxygenase (RubisCO) might possess a high specific catalytic activity. At 10% CO₂, both DSM 2625 and DSM 505 could fix CO₂ efficiently; accordingly, their cbb genes' transcription levels were much higher than those of DSM 654 and DSM 506. This result might be due to their cbb genes' relative transcription levels induced very strong responses to the increased CO₂ concentrations. Moreover, CO₂ concentrations impact on CO₂ fixing efficiency of four strains in different ways. Copyright © 2016 Elsevier Ltd.