Researchers have identified chemosynthetic bacteria in the gills of Caribbean hamlet fish, a discovery that suggests a specialized and previously unknown role for the fish gill microbiome.

Scientists from the ZMT and ICBM have discovered chemosynthetic bacteria living in the gills of hamlet fish (Hypoplectrus spp.) across the Greater Caribbean. While such bacteria are known to exist in deep-sea environments and on invertebrates, this is the first documented instance of their presence in fish. The findings, published in PLOS Genetics, indicate that fish gills host a complex, specialized microbiome distinct from the surrounding seawater.

Revisiting Genomic Data

The research team initially sequenced DNA from hundreds of gill samples to study the evolution of hamlet fish. While they originally viewed the microbial DNA as a contaminant to be discarded, they later shifted their focus to analyze the gill microbiome specifically. By reconstructing 70 bacterial genomes from 17 different groups, the researchers found that the vast majority of these microorganisms were previously unknown to science.

Metabolic Potential and Implications

The study revealed that the most widespread bacteria in the gills possess the genes necessary for chemosynthesis, a process that fixes carbon dioxide using energy from inorganic compounds rather than sunlight. Researchers suggest these bacteria may perform critical metabolic functions for the fish, potentially impacting immunity, waste excretion, and pH regulation. The team notes that this discovery opens new lines of research into how these microorganisms influence fish health in both natural populations and aquaculture.