Bacterial communities in tetrachloroethene-polluted groundwaters: a case study

Area of Science:

• Environmental microbiology
• Bioremediation
• Molecular ecology

Background:

• Chlorinated ethenes like tetrachloroethene (PCE) and trichloroethene (TCE) are common groundwater contaminants.
• Incomplete degradation leads to toxic byproducts such as cis-1,2-dichloroethene (cDCE) and vinyl chloride (VC).
• Understanding bacterial community composition is crucial for effective bioremediation.

Purpose of the Study:

• To characterize the bacterial communities, both total and active populations, in groundwater contaminated with chlorinated ethenes.
• To identify key microbial players involved in the degradation of PCE and TCE and their byproducts.
• To assess the potential of indigenous microbial consortia for bioremediation.

Main Methods:

• 16S rRNA gene pyrosequencing of DNA and RNA extracted from groundwater samples.
• Analysis of both entire and active bacterial populations across three contaminated sites.
• Long-term monitoring to assess contaminant and byproduct concentrations.

Main Results:

• Pyrosequencing identified known dechlorinating bacteria at low detection levels (<0.25%).
• Bacterial communities were dominated by a few species, with Albidiferax ferrireducens prominent across all sites.
• Active dechlorinating consortia likely include Polaromonas spp., Geobacter spp., Burkholderia spp., and Methylobacter spp.

Conclusions:

• Indigenous dechlorinating bacteria were identified in PCE and TCE contaminated groundwater.
• Albidiferax ferrireducens is a key species across diverse contamination levels.
• The identified microbial consortia offer a promising foundation for developing bioremediation strategies to degrade chloroethenes.