Examining hydrogen peroxide-containing organelles in seaweeds

Abstract

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.

Figure 1. Detection of H ₂ O ₂ -containing organelles in red, brown, and green seaweeds.

A, D, and G, snapshots of seaweed organisms used in this study - red ( Asparagopsis taxiformis ), brown ( Fucus distichus ), and green ( Ulva expansa ), respectively. Fucus distichus and Ulva expansa are imaged with a ruler . B, E, H, as negative controls, 10 mM ascorbic acid was added to quench out H ₂ O ₂ before DAB staining in Asparagopsis taxiformis , Fucus distichus , and Ulva expansa , respectively. C, F, I, DAB staining to detect H ₂ O ₂ in Asparagopsis taxiformis , Fucus distichus , and Ulva expansa , respectively. Scale bar = 30 µm