Our research asks how marine symbioses respond to environmental stress at the cellular and biochemical level.
We focus on coral bleaching and related forms of cnidarian–algal symbiosis breakdown, using reef-building corals, upside-down jellyfish, sea anemones, and Symbiodiniaceae as complementary model systems. By combining cell biology, microscopy, redox biochemistry, metabolomics, gene expression, and nanobiotechnology, we study how stress signals move between host cells and algal symbionts, and how those signals determine whether symbiosis persists or collapses.
Stress Chemistry and Coral Bleaching
Coral bleaching begins with changes in the chemical conversation between the animal host and its algal symbionts.
We study how environmental stress disrupts this relationship by altering redox balance, nitro-oxidative stress, antioxidant defenses, cellular metabolism, and immune-like signaling. By tracking these changes across cells, symbionts, and intact organisms, we aim to understand which biochemical events are early warning signs of symbiosis breakdown, and which responses help the partnership remain stable under stress.
How does redox and nitro-oxidative stress shape host–symbiont stability?
Cellular Models of Symbiosis
To understand bleaching, we need experimental systems that let us study coral biology at the scale where stress first appears: inside cells.
Our lab develops and applies cnidarian cell culture approaches, including coral-derived cells and related symbiotic model systems, to investigate host–algal interactions under controlled conditions. These cellular models allow us to test how specific stressors, nutrients, microbes, metabolites, and chemical signals affect the health of host cells and symbionts before changes are visible at the whole-organism level.
Building and using coral/cnidarian cell systems to study bleaching where it begins.
Nanobiotech for Reef Resilience
We use nanobiotechnology as both a measurement tool and a possible strategy for intervention.
Nanomaterials can help us detect, localize, and manipulate chemical processes that are difficult to observe in living symbiotic systems, including reactive oxygen and nitrogen species. By integrating nanotechnology with coral biology, microscopy, and biochemical assays, we aim to develop tools that reveal how stress moves through the symbiosis and explore whether targeted chemical approaches could help support stress tolerance.
Developing tools to measure, manipulate, and potentially mitigate stress in symbiotic systems.
Comparative Cnidarian Biology
No single organism can answer every question about coral symbiosis.
We work across reef-building corals, upside-down jellyfish, sea anemones, and Symbiodiniaceae to identify which stress responses are shared across cnidarian–algal symbioses and which are specific to particular hosts or environments. This comparative approach helps us separate general mechanisms of symbiosis from species-specific traits, making it easier to choose the right model system for each biological question.
Using corals, Cassiopea , Exaiptasia, and Symbiodiniaceae to find shared and divergent stress responses.
SPECIFIC PROJECTS
Collaborative Research:
Integrating nanobiotechnologies to understand the role of nitro-oxidative stress in the coral-dinoflagellate mutualistic symbiosis dynamics
Photo credit: Hollie Putnam
NSF award 2316389
Aug. 2023 - Jul. 2027
OVERVIEW
Although the mechanism of coral bleaching, i.e. dysbiosis between cnidarian host and algal endosymbionts, is not fully known, it is understood that a combination of excess free-radicals, a deficient antioxidant system and innate immune responses are central to the breakdown of symbiosis through cellular damage. The symbiosis between reef-building corals and dinoflagellate algae is at the center of tropical marine ecosystems which support a biodiversity rivaling that of rainforests, an economy worth US$36 billion and over 1 billion people. Environmental stress threatens symbiosis equilibrium, regulatory crosstalk, partner recognition and nutritional exchanges between host and symbiont. Recurrent mass bleaching events recorded for the last two decades have left coral reefs highly degraded, putting in question their survival past 2050. Current conservation and restoration efforts are hindered by a gap in our understanding of the molecular, cellular and microenvironmental dynamics of symbiotic dysbiosis and coral bleaching. Here we propose to integrate recent advances in cellular-level coral research, nanobiotechnology and engineering with gene expression and metabolomics to elucidate the dynamics of free-radical stress (also known as nitro-oxidative stress) and dysbiosis in cnidarian-dinoflagellate mutualistic symbiosis. While the intricacies of the coral holobiont (i.e. the coral host and its complex microbiome, algal symbiont included) are challenging because of all potential interactions between partners, our approach will strive to understand each partner’s involvement in the accumulation of free- radicals during stress on spatial scales ranging from molecules to cells and tissues to organisms. To this end, the proposed project will: (Aim 1) characterize free-radical spatio-temporal dynamic in isolation and in symbiosis; (Aim 2) characterize the cellular responsiveness to controlled, targeted nitro-oxidative stress; and (Aim 3) manipulate and track the response to nitro-oxidative stress in a 3D bionic coral model.
Project co-PIs: Hollie Putnam & Daniel Wangpraseurt
Cassiopea research
Overview: Heat shock expression in C. xamachana
The upside-down jellyfish, Cassiopea xamachana, has become a model system to understand cnidarian-dinoflagellate symbiosis as well as a potential bioindicator species for signaling declining ecosystem health. One line of research currently being pursued is to understand how this species of benthic, shallow water jellyfish responds to increase in temperatures on the cellular level.
Similar to corals, this species can also experience bleaching (the loss of symbionts) if the environment proves too stressful to support them. However unlike corals, the upside down jellyfish prefers to inhabit mangroves, where the temperatures are generally higher and the water has a higher salinity. Because of this, it is theorized that C. xamachana has a higher thermotolerance threshold, something that needs to be investigated more but could provide the knowledge needed to better help coral become more thermally resilient. To understand this, current research is being done to understand how heat shock proteins (chaperonal proteins that help combat cell death when an organism is thermally stressed) are being expressed on the cellular level when individuals of C. xamachana are exposed to temperatures higher than experienced in their natural environment. The goal is to then compare results from studies done in corals and symbiotic anemones, providing a cross model comparison to head further research.
Photo credits: Liza Roger
Artwork by: Cassandra Real
Photo credits: Liza Roger
Artwork credits: Cassandra Real
Exaiptasia model system
Overview
Exaiptasia diaphana is among the model systems used to study the cnidarian-Symbiodiniaceae symbiosis. In the lab we used E. diaphana for multi-model comparisons (with corals and upside-down jellyfish).
E. diaphana is particularly interesting as a model because its relationship with Symbiodiniaceae is facultative, meaning it can live in an aposymbiotic state (i.e., without symbionts) which allows us to study the differences between the two states.
Symbiodiniaceae research
Photo credit: Allison M. Lewis
Active culture: Breviolum minutum
We are working with B. minutum to study the biocompounds it produces in the free-living state vs the endosymbiotic state. More information soon!