Structural dynamics and transcriptomic analysis of Dehalococcoides mccartyi within a TCE-Dechlorinating community in...

Area of Science:

• Environmental microbiology
• Bioremediation
• Anaerobic respiration

Background:

• Trichloroethene (TCE) is a widespread environmental pollutant.
• Effective microbial consortia are crucial for bioremediation of chlorinated solvents.
• Understanding community dynamics under selective pressures informs bioremediation strategies.

Purpose of the Study:

• To establish and characterize a TCE-dechlorinating community (CANAS) in a flow reactor.
• To assess the long-term stability and dechlorination efficiency of CANAS.
• To investigate the microbial structure and functional gene expression supporting TCE dechlorination.

Main Methods:

• Cultivation of a TCE-dechlorinating community in a completely mixed flow reactor.
• Monitoring of TCE conversion rates and by-product formation over 400 days.
• Quantification of Dehalococcoides mccartyi populations using cell counts.
• 16S rRNA amplicon sequencing for community structure analysis.
• Transcriptomic analysis of D. mccartyi to identify key gene expression.

Main Results:

• CANAS achieved 85% TCE conversion to ethene with minimal vinyl chloride and cis-dichloroethene production.
• Two Dehalococcoides mccartyi strains were stably maintained at high cell densities.
• 16S rRNA sequencing revealed a community shift but maintained D. mccartyi abundance and functional redundancy.
• Transcriptomics identified high expression of reductive dehalogenase genes (tceA, vcrA) and hydrogenase genes (hup, vhu) in D. mccartyi.

Conclusions:

• A stable and efficient TCE-dechlorinating microbial community (CANAS) was established and maintained.
• Functional redundancy and the activity of specific reductive dehalogenases and hydrogenases are key to robust TCE dechlorination.
• This study provides insights into the microbial ecology and genetic basis of effective reductive dechlorination.