Cultivation of Chemosynthetic Symbioses

Symbiosis has transformed from a biological curiosity into a central organizing principle of life. From our gut microbiota to coral reefs, microbial partnerships drive the emergence and stability of complex ecosystems. When these relationships break down—such as in human gut dysbiosis or coral bleaching—the consequences can be severe, leading to chronic disease or ecosystem collapse.

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Our lab focuses on chemosynthetic symbioses—partnerships in which bacteria that derive energy from chemical compounds (rather than light or organic matter) support their eukaryotic hosts by fixing carbon. These systems are ecologically vital, fueling life in extreme environments like deep-sea hydrothermal vents. Yet, they remain vastly understudied compared to photosynthetic (e.g., corals) or heterotrophic (e.g., rumen) symbioses, largely due to a lack of model organisms.

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We aim to change that.

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Our research targets sulfur-oxidizing bacteria (SOB), including previously unclassified Gammaproteobacteria, that form promiscuous associations with diverse partners—ranging from ciliates to cnidarians. These SOB play key roles in sulfur cycling and likely contributed to early evolutionary innovations on Earth.

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With the support of the Moore Foundation, we develop a tractable model system, we focus on Zoothamnium niveum, a colonial ciliate covered by a monolayer of its mutualistic bacterial symbiont, Candidatus Thiobius zoothamnicola. This fast-reproducing symbiosis thrives in shallow, sulfidic marine environments. The host receives fixed carbon from the bacteria, while the symbionts gain access to sulfide and oxygen via the ciliate’s behavior.

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While Z. niveum has been cultivated in the lab, previous methods relied on expensive and technically demanding flow-through chambers, limiting access and reproducibility. To address this, we’ve engineered a new low-cost cultivation device. Our system uses 3D-printed molds to cast PDMS chambers incorporating a static mixer that ensures the mingling of sulfide-rich and oxygenated seawater. 

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By democratizing cultivation tools, we hope to make Z. niveum a widely adopted model for studying chemosynthetic symbiosis—unlocking new insights into host-microbe interactions, microbial metabolism, and the evolution of cooperation.