Identification of CO₂ induces oxidative stress to change bacterial surface properties

The surface properties of bacteria play an essential role in their abilities to perform transmembrane communication, adherence, immobilization, flocculation, etc. However, the responsiveness of bacterial surfaces to elevated atmospheric CO₂ remains unknown. In this study, using the model bacteria, Paracoccus denitrificans, the effect of CO₂ on the primary bacterial surface properties, specifically hydrophobicity and surface charge, has been explored. We found that hydrophilicity and negative surface charge both rose in conjunction with increased atmospheric CO₂ concentrations. Studies of the potential mechanisms involved have illustrated that elevated CO₂ significantly increases the production of polysaccharides in extracellular polymeric substances (EPS). Various hydrophilic groups and negative charges in these polysaccharides prompt hydrophilicity and surface charge variations in bacteria. Further research has identified that elevations in CO₂ result in the accumulation of reactive species, specifically reactive nitrogen species (RNS). In this study, it was found that RNS damaged the permeability of bacterial membranes by inducing lipid peroxidation and then caused the leakage of intracellular substrate, which ultimately led to an increase in EPS polysaccharides. Our findings suggest that changes in bacterial surface properties due to atmospheric CO₂ elevation, as well as the reactions these trigger, merit widespread attention.