Boosting anaerobic reductive dehalogenation with natural protein amendments to unlock cryptic organohalide-reducing bacteria.

Deep-sea sediments host a rich yet largely unexplored reservoir of microorganisms capable of reductive dehalogenation. However, the activity of dehalogenating consortia is often limited even under carbon-rich conditions, impeding the identification of key functional players. In this study, we report that the addition of natural protein materials can dramatically stimulate reductive dehalogenation in an enrichment culture derived from deep-sea cold seep sediments. This stimulatory effect was clearly demonstrated by supplementation with bovine serum albumin (BSA), which significantly enhanced the degradation rates of 2,4,6-tribromophenol (2,4,6-TBP) and tetrachloroethene (PCE). Integrated metagenomic and metatranscriptomic analyses revealed that two candidate novel clostridial lineages-Romboutsia and Oxobacteraceae-present in BSA-amended cultures harbored distinct reductive dehalogenase (RDase) genes. Romboutsia harbored three RDase genes, with one being upregulated during the degradation of 2,4,6-TBP intermediates and another specifically responding to PCE, suggesting a substrate-dependent regulatory strategy. Oxobacteraceae encoded a cytosolic RDase that was highly expressed during 2,4,6-TBP transformation. Metabolic reconstruction further indicated that both lineages could utilize BSA-derived amino acids for growth. This work establishes an effective biostimulation strategy to activate dehalogenation in deep-sea microbial communities and expands the known diversity and functional versatility of candidate organohalide-reducing bacteria.