Plasmid-controlled mercury biotransformation by Clostridium cochlearium T-2

Area of Science:

• Microbiology
• Environmental Science
• Biochemistry

Background:

• Mercury compounds are significant environmental pollutants.
• Bacterial mercury biotransformation plays a crucial role in mercury cycling.
• Understanding the genetic basis of mercury metabolism is vital for bioremediation strategies.

Purpose of the Study:

• To isolate and characterize Clostridium cochlearium with methylmercury-decomposing ability.
• To investigate the genetic basis of mercury biotransformation in this bacterial strain.
• To elucidate the role of plasmids in controlling mercury methylation and demethylation.

Main Methods:

• Isolation and culturing of Clostridium cochlearium.
• Treatment with acridine dye to cure plasmid-mediated traits.
• Bacterial conjugation to restore traits.
• Agarose gel electrophoresis to analyze DNA.
• Assay of methylmercury decomposition and mercuric ion methylation.

Main Results:

• A Clostridium cochlearium strain capable of methylmercury decomposition was isolated.
• Plasmid loss (curing) resulted in loss of demethylation and gain of methylation activity.
• Plasmid reintroduction via conjugation restored methylmercury-decomposing ability.
• Agarose gel electrophoresis indicated plasmid involvement in mercury biotransformation.

Conclusions:

• Plasmids in Clostridium cochlearium control mercury biotransformation in opposing directions: methylation and demethylation.
• The presence of the plasmid is associated with mercury demethylation, while its absence is linked to methylation.
• A potential mechanism for mercury resistance involving hydrogen sulfide is proposed.