Nickel accumulation by the green algae-like Euglena gracilis

Area of Science:

• Environmental toxicology
• Cellular biology
• Biochemistry

Background:

• Nickel is a heavy metal with potential toxicity to aquatic organisms.
• Understanding nickel's impact on phytoplankton is crucial for aquatic ecosystem health.
• Euglena gracilis is a model organism for studying environmental stress responses.

Purpose of the Study:

• To investigate nickel accumulation in Euglena gracilis.
• To determine the effects of nickel on cellular growth, respiration, and photosynthesis.
• To analyze the role of thiols, histidine, and phosphate molecules in nickel tolerance.

Main Methods:

• Exposure of Euglena gracilis to various nickel chloride concentrations.
• Measurement of oxygen consumption, photosynthesis rates, and chlorophyll content.
• Quantification of cellular thiols, histidine, and phosphate molecules.

Main Results:

• Nickel exposure (0.5-1mM NiCl2) impaired oxygen consumption, photosynthesis, and APX activity, but not cellular integrity.
• Magnesium and copper ions reduced nickel accumulation, while other divalent cations were innocuous.
• Maximal nickel accumulation (1362mg/Kg DW) occurred at 1mM Ni2+ without Mg2+ or Cu2+; thiols, histidine, and phosphates showed moderate involvement.

Conclusions:

• Euglena gracilis exhibits significant nickel accumulation capacity.
• Nickel toxicity is modulated by external magnesium and copper concentrations.
• Cellular defense mechanisms involving thiols, histidine, and phosphates contribute moderately to nickel tolerance.