Genome-resolved transcriptomics reveals novel PCE-dehalogenating bacteria from Aarhus Bay sediments.

Area of Science:

• Microbiology and Environmental Science
• Bioremediation and Biogeochemical Cycling

Background:

• Organohalide-respiring bacteria (OHRB) are crucial for bioremediation and natural halogen cycling.
• Existing knowledge of OHRB is limited to specific genera; novel OHRB in natural environments are largely uncharacterized.

Purpose of the Study:

• To identify and characterize novel OHRB from tetrachloroethene-respiring cultures.
• To investigate the activity and regulation of reductive dehalogenase (RDase) genes in these newly identified OHRB.

Main Methods:

• Genome-resolved transcriptomic analysis combining short- and long-read sequencing.
• Assembly of 37 medium-quality bacterial bins from marine sediment enrichments.
• Metatranscriptomic analysis to assess gene expression and regulatory mechanisms.

Main Results:

• Identified 16 bacterial bins containing RDase genes, affiliated with phyla not previously known for reductive dehalogenation (Bacteroidota, Synergistota, Spirochaetota).
• Discovered a novel OHRB (bin.26) with 97 RDase genes, 84 of which were transcribed during tetrachloroethene dechlorination.
• Revealed that RDase gene expression is potentially regulated by stress-responsive transcriptional regulators (HrcA, SigW).

Conclusions:

• This study pinpoints novel OHRB from pristine marine environments, significantly broadening the known diversity of dehalogenating bacteria.
• The findings enhance understanding of the activity and diverse regulatory systems governing RDase genes in natural halogen cycling.
• The research contributes to a more comprehensive view of microbial roles in global organohalide transformations.