Metabolic handoffs between multiple symbionts of deep-sea mussel Idas modiolaeformis

Bathymodioline mussels rely on thiotrophic and methanotrophic chemosynthetic symbionts for nutrition, yet, secondary heterotrophic symbionts are often present and play an unknown role in the fitness of the organism. Here we curated metagenome-assembled genomes of I. modiolaeformis symbionts and used genome-centered metatranscriptomics and metaproteomics to assess the key functions of the secondary symbionts. Our findings indicate that these flexible associations allow for expanding the range of substrates and environmental niches, via new metabolic functions and handoffs.