Stable Function, Dynamic Phylotypes: Microdiversity as a Reservoir for Resilience in Dehalococcoides.

Area of Science:

• Environmental microbiology
• Bioremediation
• Halogen cycling

Background:

• Organohalide-respiring bacteria (OHRB) are vital for halogen cycling and pollutant degradation but face challenges like slow growth.
• Dehalococcoides, a key OHRB, exhibits declining abundance and gene loss in bioaugmentation, impacting functional stability.
• Mechanisms supporting long-term OHRB functional stability are not fully understood.

Purpose of the Study:

• To investigate the role of strain-level microdiversity in Dehalococcoides for community-scale dehalogenation resilience.
• To understand how genetic variation within Dehalococcoides populations contributes to functional stability under cultivation.

Main Methods:

• Reconstruction of a Dehalococcoides consortium (AEDhc) from eight enrichment cultures.
• Sequencing of a Dehalococcoides-specific marker gene to identify coexisting phylotypes.
• Proteomics analysis to identify expressed reductive dehalogenase (RDase) genes.

Main Results:

• AEDhc harbored 30 distinct Dehalococcoides phylotypes.
• The consortium consistently debrominated tetra- and pentabrominated diphenyl ethers without intermediate accumulation.
• Expression of RDase genes was dominated by PcbA1-like and TceA-like RDases across transfers, despite phylotype abundance fluctuations.

Conclusions:

• Coexistence and dynamic fluctuations of Dehalococcoides phylotypes enhance functional stability and ecological resilience.
• Genetic variation within Dehalococcoides serves as a reservoir of metabolic potential for sustained dehalogenation.
• Strain-level heterogeneity is critical for effective bioremediation strategies using OHRB.