Biodegradation of hexachlorobenzene by a constructed microbial consortium

Area of Science:

• Environmental Microbiology
• Bioremediation
• Synthetic Biology

Background:

• Hexachlorobenzene (HCB) is a persistent organic pollutant with significant environmental and health risks.
• Current bioremediation strategies for HCB are limited due to its recalcitrant nature.
• Microbial degradation offers a potential solution for HCB contamination.

Purpose of the Study:

• To develop a microbial consortium for efficient hexachlorobenzene (HCB) degradation.
• To engineer a bacterial strain capable of initiating HCB breakdown into a more manageable intermediate.
• To assess the efficacy of a co-culture system for complete HCB remediation.

Main Methods:

• Construction of an engineered Escherichia coli strain (DH5α) expressing a cytochrome P450cam (CYP101) mutant for HCB oxidation.
• Co-culturing the engineered E. coli with Sphingobium chlorophenolicum ATCC 39723, a natural pentachlorophenol (PCP) degrader.
• Utilizing gas chromatography to monitor HCB degradation and PCP accumulation/consumption.

Main Results:

• The E. coli/S. chlorophenolicum consortium degraded approximately 40% of 4 μM HCB in 24 hours.
• The engineered E. coli successfully converted HCB to PCP, which was then completely degraded by S. chlorophenolicum.
• A control consortium using Pseudomonas putida PaW340 showed limited PCP degradation, suggesting transport barriers.

Conclusions:

• A bacterial co-culture strategy involving engineered E. coli and S. chlorophenolicum is effective for HCB bioremediation.
• The engineered E. coli initiates HCB degradation, and S. chlorophenolicum completes the process, overcoming PCP accumulation issues.
• This approach offers a viable alternative for the treatment of HCB-contaminated environments.