Resistance of urea hydrolytic bacteria to Hg2+ probed by single injection isothermal titration calorimetry

Abstract:

[Objective] To determine the resistance of urea hydrolytic bacteria to Hg2+ using single injection isothermal titration calorimetry (SIITC). [Methods] The tolerance of urea hydrolytic bacterium Staphylococcus succinus to Hg2+ toxicity was assessed by SIITC in comparison with the traditional cell growth curves and pH change curves. The correlation between SIITC and the traditional methods was examined. [Results] The maximum heat flux rate and the accumulated heat of adsorption and hydrolysis of urea by S. succinus decreased with increasing Hg2+ concentration up to 10 μmol/L. The maximum heat flux rate decreased from ?45 μJ/s for the control to ?20 μJ/s for 10 μmol/L Hg2+ treated cells and the accumulated heat decreased from ?1 291.90 μJ for the control to ?535.75 μJ for 10 μmol/L Hg2+ treated cells. The decreases of heat flux rate and accumulated heat well correlated with the change of solution pH (r=0.928) and cell growth rate OD600 (r=0.955). [Conclusion] SIITC is a potential method to detect tolerance of bacteria to Hg2+.

Key words:Urea hydrolytic bacteria, heavy metals, bioremediation, toxicity test, single injection isothermal titration calorimetry