Examining hydrogen peroxide-containing organelles in seaweeds.

Seaweeds, particularly the red seaweed Asparagopsis taxiformis , produce and sequester bromomethanes, which are known for mitigating methane emissions in ruminants when used as a feed supplement. Bromomethane synthesis requires hydrogen peroxide (H ₂ O ₂ ). We developed a staining assay utilizing 3,3'-diaminobenzidine (DAB) for identifying H ₂ O ₂ in three groups of seaweeds (red, brown, and green), including intensely pigmented species. Our findings indicate the previously identified "gland cell" in Asparagopsis taxiformis , responsible for bromoform synthesis and retention, is a specialized large organelle rich in H ₂ O ₂ . Our study introduces an effective survey tool to identify promising seaweed species abundant in bromoform from diverse marine habitats.