Study sheds light on deep-sea tubeworm symbiosis
A recent study has unveiled the intricate relationship between deep-sea chemosynthetic tubeworms and their symbiotic bacteria. Conducted by researchers from the Institute of Oceanology of the Chinese Academy of Sciences and the Hong Kong University of Science and Technology, the study utilised advanced single-cell RNA sequencing technology to explore the complex interactions within the tubeworm Paraescarpia echinospica.
These tubeworms thrive in extreme environments like hydrothermal vents and cold seeps—areas on the ocean floor where gases like methane and hydrogen sulphide escape from the seabed. The worms lack a digestive system and rely entirely on sulphide-oxidising bacteria housed in a specialised organ called the trophosome. Within the trophosome are bacteriocytes, specialised cells that house the symbiotic bacteria. The researchers developed an innovative deep-sea in situ single-cell fixation system, allowing them to construct a detailed cellular atlas of the trophosome.
The findings, published in Science Advances with Dr Hao Wang as the first author, reveal distinct cell populations within the trophosome that express genes related to gas transport and metabolite shuttling. This suggests the formation of a biochemical gradient that facilitates the delivery of chemosynthetic substrates from the periphery to the centre of the trophosome.
The researchers found two distinct bacteriocyte populations within each segment of the trophosome, occupying separate microenvironments. The oxygen-rich periphery bacteriocytes are involved in carbon fixation, while those in the centre, where oxygen is scarce, convert nitrates into gas, potentially aiding in ammonia waste elimination.
This spatial organisation within the trophosome offers new insights into symbiosis and environmental adaptation in deep-sea organisms. And the study's use of a new deep-sea in situ single-cell fixation system will potentially advance our understanding of biological adaptation in a variety of marine animals.