Deep-Sea Corals and Feather Stars Share 'Promiscuous' Microbes

The deep ocean floor is a challenging place to live, yet corals and crinoids, also known as feather stars, often thrive together. The nature of their relationship has long been a mystery, but a new study from Brazil’s Campos Basin offers a microbial explanation. Researchers found that different species of corals and the crinoids living with them host identical communities of symbiotic microorganisms.

This unusual sharing, or 'promiscuity', is centred around a newly discovered bacterium, Endozoicomonas promiscua. Genomic analysis revealed this microbe performs a vital function called dissimilatory nitrate reduction to ammonia (DNRA), essentially converting one form of nitrogen into ammonia. This ammonia then serves as a crucial resource for other microbes living within both the corals and the crinoids.

This cooperative behaviour creates a cross-host nitrogen-cycling network. Such microbial versatility suggests a sophisticated strategy for resilience, where shared metabolic capabilities help the entire biological community thrive in the nutrient-limited darkness of the deep sea and contribute to wider ocean biogeochemical cycles.