Removal of mercury(II), lead(II) and cadmium(II) from aqueous solutions using Rhodobacter sphaeroides SC01

Area of Science:

• Environmental Microbiology
• Bioremediation
• Heavy Metal Toxicology

Background:

• Microorganisms are effective in removing heavy metals from solutions.
• Investigating Rhodobacter sphaeroides SC01's response to heavy metal stress is crucial for bioremediation applications.

Purpose of the Study:

• To evaluate the heavy metal removal efficiency of Rhodobacter sphaeroides SC01.
• To understand the oxidative damage, antioxidant responses, and removal mechanisms of SC01 under mercury, lead, and cadmium stress.
• To assess the potential of SC01 for lead removal from industrial effluents.

Main Methods:

• Exposure of Rhodobacter sphaeroides SC01 to mercury, lead, and cadmium.
• Quantification of removal rates, reactive oxygen species (ROS) levels, and cell death.
• Measurement of antioxidant enzyme activities.
• Fourier transform infrared spectroscopy (FTIR) and X-ray diffraction (XRD) analysis for mechanism investigation.

Main Results:

• SC01 exhibited a high Pb removal rate (98%), outperforming mercury and cadmium removal.
• Pb stress induced lower ROS levels and cell death compared to Hg and Cd stress.
• Antioxidant enzyme activities were higher under Pb stress than under Hg or Cd stress.
• FTIR indicated Pb complexation with hydroxyl, amid, and phosphate groups.
• XRD revealed the formation of lead phosphate hydroxide precipitate on the cell surface.

Conclusions:

• Rhodobacter sphaeroides SC01 demonstrates significant potential for lead bioremediation.
• Biosorption and precipitation are key mechanisms for lead removal by SC01.
• SC01's robust antioxidant system contributes to its tolerance and efficiency in lead-contaminated environments.