Biology subjects

Suggett, D. J.

Publications and source records attributed to Suggett, D. J..

6 recordsLinked to original sources

bioRxiv2026

Colony geometric complexity predicts the co-occurrence of coral photosymbiont genera

The endosymbiosis between tropical reef-building corals and dinoflagellate algae (family Symbiodiniaceae) underpins the healthy functioning of coral reef ecosystems. Although dominant host-symbiont pairings differ across spatial scales (e.g., bioregion, reef zone, and depth), corals often associate with multiple symbionts. Where diverse symbionts occur together, their local-scale ecology is poorly understood. Moreover, whilst coral morphological plasticity generates a structurally complex spatial habitat for endosymbiosis, the role of host geometry in facilitating symbiont co-occurrence is completely unexplored. Here, we integrated high-throughput sequencing of the ITS2 gene region with digital 3D photogrammetry to evaluate symbiont distribution within coral structural habitat and determine the influence of host morphology on symbiont community composition. Symbiont composition was characterised along a vertical gradient (coral apex to base) across 50 Hydnophora microconos colonies from Rarotonga, Cook Islands. We identified dominance by the genera Durusdinium and Cladocopium, with inter-genus co-occurrence recognised in 60% of coral colonies. The co-occurrence of two Cladocopium lineages (C3f and C3k) was validated based on congruence with the plastid minicircle psbA non-coding region (psbAncr). Geometric quantification from digital 3D reconstructions of coral colonies revealed that single symbiont taxon colonies were morphologically distinct, whilst multi-symbiont colonies exhibited a broader morphological range. Where Cladocopium-Durusdinium co-occurrence was identified, surface orientation indicated increased Durusdinium prevalence toward the base of coral colonies, corresponding to regions with the highest occlusion of modelled downwelling light. Collectively, these findings suggest that coral structural heterogeneity supports Symbiodiniaceae diversity and highlights the value of resolving microhabitat-level variation to understand symbiont co-occurrence.

ecology↗

bioRxiv2025

Lipid nanoparticle supplementation enhances host metabolism in a model symbiotic cnidarian

Stable cnidarian-dinoflagellate symbiosis provides the trophic foundation of coral reef ecosystems. Understanding nutrient exchange underpinning this symbiosis grows increasingly urgent as reefs face accelerating threats from climate change, and the need for time-critical interventions to improve coral health via aquaculture. Lipid nanoparticles (LNPs), widely used as delivery vehicles in biomedical science, are emerging as a promising tool to supplement coral nutrition. However, physiological impacts of LNPs on cnidarians, including uptake, nutritional value, and holobiont response, remain largely unexplored. Here, we delivered empty, phosphatidylcholine LNPs to both symbiotic and aposymbiotic Exaiptasia diaphana, an anemone model for corals, and analyzed the host proteomic response via mass spectrometry. LNP supplementation elicited broad proteome shifts, with notable overlap between symbiosis- and LNP-induced protein expression. Proteins involved in lipid catabolism, lipid transport, {beta}-oxidation, lysosomal function, and protein translation were significantly more abundant, consistent with enhanced lipid processing and metabolic activity. LNP supplementation, like symbiosis, suppressed both asexual reproduction and the expression of a suite of predation- and digestion-associated venom proteins and proteases, suggesting a conserved "sated" phenotype in response to lipid supply. Variations in feeding frequency with Artemia had minimal impact, indicating that LNPs can be a robust supplement irrespective of primary feeding regime. These data demonstrate that adult Exaiptasia are capable of direct uptake of LNPs, offering a tool for probing lipid metabolism, signaling and symbiotic function in cnidarians. Moreover, the ability to manipulate host physiology using defined lipid formulations holds significant potential for advancing coral aquaculture stress resilience, including reef restoration strategies.

zoology↗

bioRxiv2024

Octadecanoids as emerging lipid mediators in cnidarian-dinoflagellate symbiosis

Oxylipin signaling has been suggested as a potential mechanism for the inter-partner recognition and homeostasis regulation of cnidarian-dinoflagellate symbiosis, which maintains the ecological viability of coral reefs. Here we assessed the effects of symbiosis and symbiont identity on a model cnidarian, the sea anemone Exaiptasia diaphana, using mass spectrometry to quantify octadecanoid oxylipins (i.e., 18-carbon-derived oxygenated fatty acids). A total of 84 octadecanoids were reported, and distinct stereospecificity was observed for the synthesis of R- and S-enantiomers for symbiont-free anemones and free-living cultured dinoflagellate symbionts, respectively. Symbiont-derived 13(S)-hydroxy-octadecatetraenoic acid (13(S)- HOTE) linked to a 13S-lipoxygnase was translocated to the host anemone with a 32-fold increase, suggesting it as a biomarker of symbiosis and as a potential agonist of host receptors that regulate inflammatory transcription. Only symbiosis with the native symbiont Breviolum minutum decreased the abundance of pro-inflammatory 9(R)-hydroxy-octadecadienoic acid (9(R)-HODE) in the host. In contrast, symbiosis with the non-native symbiont Durusdinium trenchii was marked by higher abundance of autoxidation-derived octadecanoids, corroborating previous evidence for cellular stress in this association. The putative octadecanoid signaling pathways reported here suggest foundational knowledge gaps that can support the bioengineering and selective breeding of more optimal host-symbiont pairings to enhance resilience and survival of coral reefs.

biochemistry↗

bioRxiv2024

Microscale sampling of the coral gastric cavity reveals a gut-like microbial community

Animal guts contain numerous microbes, which are critical for nutrient assimilation and pathogen defence. While corals and other Cnidaria lack a true differentiated gut, they possess gastrovascular cavities (GVCs), semi-enclosed compartments where vital processes such as digestion, reproduction and symbiotic exchanges take place. The microbiome harboured in GVCs is therefore likely key to holobiont fitness, but remains severely understudied due to challenges of working in these small compartments. Here, we developed minimally invasive methodologies to sample the GVC of coral polyps and characterise the microbial communities harboured within. We used glass capillaries, low dead volume microneedles, or nylon microswabs to sample the gastric microbiome of individual polyps from six species of corals, then applied low-input DNA extraction to characterise the microbial communities from these microliter volume samples. Microsensor measurements of GVCs revealed anoxic or hypoxic micro-niches, which persist even under prolonged illumination with saturating irradiance. These niches harboured microbial communities enriched in putatively microaerophilic or facultatively anaerobic taxa, such as Epsilonproteobacteria. Some core taxa found in the GVC of Lobophyllia hemprichii from the Great Barrier Reef were also detected in conspecific colonies held in aquaria, indicating that these associations are unlikely to be transient. Our findings suggest that the coral GVC is chemically and microbiologically similar to the gut of higher Metazoa. Given the importance of gut microbiomes in mediating animal health, harnessing the coral "gut microbiome" may foster novel active interventions aimed at increasing the resilience of coral reefs to the climate crisis.

microbiology↗

bioRxiv2022

Whole-genome duplication in an algal symbiont serendipitously confers thermal tolerance to corals

The algal endosymbiont Durusdinium trenchii enhances the resilience of coral reefs under thermal stress1,2. As an endosymbiont, D. trenchii is generally expected to have a reduced genome compared to its free-living relatives, due in part to the lack of selective pressure for maintaining redundant gene functions in a stable intracellular environment within the host3. However, D. trenchii can live freely or in endosymbiosis, and the analysis of genetic markers4 suggests that this species has undergone whole-genome duplication (WGD). Here we present genome assemblies for two D. trenchii isolates, confirm WGD in these taxa, and examine how selection has shaped the duplicated genome regions. We assess how the competing free-living versus endosymbiotic lifestyles of D. trenchii have contributed to the retention and divergence of duplicated genes, and how these processes have enhanced thermotolerance of corals hosting these symbionts. We find that lifestyle is the driver of post-WGD evolution in D. trenchii, with the free-living phase being most important, followed by endosymbiosis. Adaptations to both lifestyles collectively result in increased cellular fitness for D. trenchii, which provides enhanced thermal stress protection to the host coral. Beyond corals, this polyploid alga is a valuable model for understanding how genome-wide selective forces act to balance the often, divergent constraints imposed by competing lifestyles.

genomics↗

bioRxiv2021

Chlorophyll fluorescence-based estimates of photosynthetic electron transport in Arctic phytoplankton assemblages

We employed Fast Repetition Rate fluorometry for high-resolution mapping of marine phytoplankton photophysiology and primary productivity in the Lancaster Sound and Barrow Strait regions of the Canadian Arctic Archipelago in the summer of 2019. Continuous ship-board analysis of chlorophyll a variable fluorescence demonstrated relatively low photochemical efficiency over most of the cruise-track, with the exception of localized regions within Barrow Strait where there was increased vertical mixing and proximity to land-based nutrient sources. Along the full transect, we observed strong non-photochemical quenching of chlorophyll fluorescence, with relaxation times longer than the 5-minute period used for dark acclimation. Such long-term quenching effects complicate continuous underway acquisition of fluorescence amplitude-based estimates of photosynthetic electron transport rates, which rely on dark acclimation of samples. As an alternative, we employed a new algorithm to derive electron transport rates based on analysis of fluorescence relaxation kinetics, which does not require dark acclimation. Direct comparison of kinetics- and amplitude-based electron transport rate measurements demonstrated kinetic-based estimates were, on average, 2-fold higher than amplitude-based values. The magnitude of decoupling between the two electron transport rate estimates increased in association with photophysiological diagnostics of nutrient stress. Discrepancies between electron transport rate estimates likely resulted from the use of different photophysiological parameters to derive the kinetics- and amplitude-based algorithms, and choice of numerical model used to fit variable fluorescence curves and analyze fluorescence kinetics under actinic light. Our results highlight environmental and methodological influences on fluorescence-based productivity estimates, and prompt discussion of best-practices for future underway fluorescence-based efforts to monitor phytoplankton photosynthesis.

plant biology↗