Spherulization as a process for the exudation of chemical cues by the encrusting sponge C. crambe

In Situ Capture and Real-Time Enrichment of Marine Chemical Diversity

Analyzing the chemical composition of seawater to understand its influence on ecosystem functions is a long-lasting challenge due to the inherent complexity and dynamic nature of marine environments. Describing the intricate chemistry of seawater requires optimal in situ sampling. Here is presented a novel underwater hand-held solid-phase extraction device, I-SMEL (In Situ Marine moleculELogger), which aims to concentrate diluted molecules from large volumes of seawater in a delimited zone targeting keystone benthic species. Marine benthic holobionts, such as sponges, can impact the chemical composition of their surroundings possibly through the production and release of their specialized metabolites, hence termed exometabolites (EMs). I-SMEL was deployed in a sponge-dominated Mediterranean ecosystem at a 15 m depth. Untargeted MS-based metabolomics was performed on enriched EM extracts and showed (1) the chemical diversity of enriched seawater metabolites and (2) reproducible recovery and enrichment of specialized sponge EMs such as aerothionin, demethylfurospongin-4, and longamide B methyl ester. These EMs constitute the chemical identity of each targeted species: Aplysina cavernicola, Spongia officinalis, and Agelas oroides, respectively. I-SMEL concentrated sponge EMs from 10 L of water in a 10 min sampling time. The present proof of concept with I-SMEL opens new research perspectives in marine chemical ecology and sets the stage for further sustainable efforts in natural product chemistry.

Regeneration in calcareous sponge relies on 'purse-string' mechanism and the rearrangements of actin cytoskeleton

The crucial step in any regeneration process is epithelization, i.e. the restoration of an epithelium structural and functional integrity. Epithelization requires cytoskeletal rearrangements, primarily of actin filaments and microtubules. Sponges (phylum Porifera) are early branching metazoans with pronounced regenerative abilities. Calcareous sponges have a unique step during regeneration: the formation of a temporary structure, called regenerative membrane which initially covers a wound. It forms due to the morphallactic rearrangements of exopinaco- and choanoderm epithelial-like layers. The current study quantitatively evaluates morphological changes and characterises underlying actin cytoskeleton rearrangements during regenerative membrane formation in asconoid calcareous sponge Leucosolenia variabilis through a combination of time-lapse imaging, immunocytochemistry, and confocal laser scanning microscopy. Regenerative membrane formation has non-linear stochastic dynamics with numerous fluctuations. The pinacocytes at the leading edge of regenerative membrane form a contractile actomyosin cable. Regenerative membrane formation either depends on its contraction or being coordinated through it. The cell morphology changes significantly during regenerative membrane formation. Exopinacocytes flatten, their area increases, while circularity decreases. Choanocytes transdifferentiate into endopinacocytes, losing microvillar collar and flagellum. Their area increases and circularity decreases. Subsequent redifferentiation of endopinacocytes into choanocytes is accompanied by inverse changes in cell morphology. All transformations rely on actin filament rearrangements similar to those characteristic of bilaterian animals. Altogether, we provide here a qualitative and quantitative description of cell transformations during reparative epithelial morphogenesis in a calcareous sponge.

Diving into the Molecular Diversity of Aplysina cavernicola's Exometabolites: Contribution of Bromo-Spiroisoxazoline Alkaloids

Sponges are prolific producers of specialized metabolites with unique structural scaffolds. Their chemical diversity has always inspired natural product chemists working in drug discovery. As part of their metabolic filter-feeding activities, sponges are known to release molecules, possibly including their specialized metabolites. These released "Exo-Metabolites" (EMs) may be considered as new chemical reservoirs that could be collected from the water column while preserving marine biodiversity. The present work aims to determine the proportion and diversity of specialized EMs released by the sponge Aplysina cavernicola (Vacelet 1959). This Mediterranean sponge produces bromo-spiroisoxazoline alkaloids that are widely distributed in the Aplysinidae family. Aquarium experiments were designed to facilitate a continuous concentration of dissolved and diluted metabolites from the seawater around the sponges. Mass Spectrometry (MS)-based metabolomics combined with a dereplication pipeline were performed to investigate the proportion and identity of brominated alkaloids released as EMs. Chemometric analysis revealed that brominated features represented 12% of the total sponge's EM features. Consequently, a total of 13 bromotyrosine alkaloids were reproducibly detected as EMs. The most abundant ones were aerothionin, purealidin L, aerophobin 1, and a new structural congener, herein named aplysine 1. Their structural identity was confirmed by NMR analyses following their isolation. MS-based quantification indicated that these major brominated EMs represented up to 1.0 ± 0.3% w/w of the concentrated seawater extract. This analytical workflow and collected results will serve as a stepping stone to characterize the composition of A. cavernicola's EMs and those released by other sponges through in situ experiments, leading to further evaluate the biological properties of such EMs.

Sponges present a core prokaryotic community stable across Tropical Western Atlantic

Sponges are among the earliest lineages of metazoans, with first fossil records dated back to 890 million years ago. All sponge species present associations with microorganisms to some extension, which influence sponges' survival and adaptation. Sponge species can be divided into two categories, Low Microbial Abundance and High Microbial Abundance, depending on the abundance of the microbial community that they host. Monanchora arbuscula (a Low Microbial Abundance sponge species) and Xestospongia muta (a High Microbial Abundance sponge species) are sponges with widespread distribution in the Tropical Western Atlantic. Despite previous studies on the major features of these species, little is known whether M. arcuscula and X. muta prokaryotic communities are stable across vast geographic regions. We obtained a total of ~9.26 million 16S rRNA gene Illumina sequences for M. arbuscula samples collected at seven locations and for X. muta samples collected at three locations, corresponding to five ecoregions of the Caribbean and the Southwestern Atlantic (N = 105, 39 from M. arcuscula and 66 from X. muta). These samples reflected different ecological strategies for prokaryotic communities assembly, since the core prokaryotic communities of M. arbuscula are more heterotrophic and shared with different sources (corals, sponges, seawater, sediments), while X. muta has more significant photosynthetic prokaryotic communities, mainly outsourced from other sponges. Results of M. arbuscula and X. muta prokaryotic communities analysis demonstrate that both sponge species have core prokaryotic communities stable across a vast geographic area (> 8000 km), and the world's most notable coastal marine biogeographic filter, the Amazon River Mouth, in spite of the significant differences found among transient prokaryotic communities of both sponge species.

Barrettides: A Peptide Family Specifically Produced by the Deep-Sea Sponge Geodia barretti

Natural product discovery by isolation and structure elucidation is a laborious task often requiring ample quantities of biological starting material and frequently resulting in the rediscovery of previously known compounds. However, peptides are a compound class amenable to an alternative genomic, transcriptomic, and in silico discovery route by similarity searches of known peptide sequences against sequencing data. Based on the sequences of barrettides A and B, we identified five new barrettide sequences (barrettides C-G) predicted from the North Atlantic deep-sea demosponge Geodia barretti (Geodiidae). We synthesized, folded, and investigated one of the newly described barrettides, barrettide C (NVVPCFCVEDETSGAKTCIPDNCDASRGTNP, disulfide connectivity I-IV, II-III). Co-elution experiments of synthetic and sponge-derived barrettide C confirmed its native conformation. NMR spectroscopy and the anti-biofouling activity on larval settlement of the bay barnacle Amphibalanus improvisus (IC50 0.64 μM) show that barrettide C is highly similar to barrettides A and B in both structure and function. Several lines of evidence suggest that barrettides are produced by the sponge itself and not one of its microbial symbionts.

Human impacts on deep-sea sponge grounds: Applying environmental omics to monitoring

Sponges (Phylum Porifera) are the oldest extant Metazoans. In the deep sea, sponges can occur at high densities forming habitats known as sponge grounds. Sponge grounds can extend over large areas of up to hundreds of km² and are biodiversity hotspots. However, as human activities, including deep-water hydrocarbon extraction, continue to expand into areas harbouring sponge grounds, understanding how anthropogenic impacts affect sponges and the ecosystem services they provide at multiple biological scales (community, individual and (sub)cellular levels) is key for achieving sustainable management. This chapter (1) provides an update to the chapter of Advances in Marine Biology Volume 79 entitled "Potential Impacts of Offshore Oil and Gas Activities on Deep-Sea Sponges and the Habitats They Form" and (2) discusses the use of omics as a future tool for deep-sea ecosystem monitoring. While metagenomics and (meta)transcriptomics studies have contributed to improve our understanding of sponge biology in recent years, metabolomics analysis has mostly been used to identify natural products. The sponge metabolome, therefore, remains vastly unknown despite the fact that the metabolome is a key link between the genotype and phenotype, giving us a unique new insight to how key components of an ecosystem are functioning. As the fraction of the metabolome released into the seawater, the sponge exometabolome has only just started to be characterised in comparative environmental metabolomic studies. Yet, the sponge exometabolome constitute a unique opportunity for the identification of biomarkers of sponge health as compounds can be measured in seawater, bypassing the need for physical samples which can still be difficult to collect in the deep sea. Within sponge grounds, the characterisation of a shared sponge exometabolome could lead to the identification of biomarkers of ecosystem functioning and overall health. Challenges remain in establishing omics approaches in environmental monitoring but constant technological advances and reduction in costs means these techniques will become widely available in the future.

From waste of marine culture to natural patch in cardiac tissue engineering

Sea squirt, as a highly invasive species and main biofouling source in marine aquaculture, has seriously threatened the biodiversity and aquaculture economy. On the other hand, a conductive biomaterial with excellent biocompatibility, and appropriate mechanical property from renewable resources is urgently required for tissue engineering patches. To meet these targets, we presented a novel and robust strategy for sustainable development aiming at the marine pollution via recycling and upgrading the waste biomass-sea squirts and serving as a renewable resource for functional bio-scaffold patch in tissue engineering. We firstly demonstrated that the tunic cellulose derived natural self-conductive scaffolds successfully served as functional cardiac patches, which significantly promote the maturation and spontaneous contraction of cardiomyocytes both in vitro and enhance cardiac function of MI rats in vivo. We believe this novel, feasible and “Trash to Treasure” strategy to gain cardiac patches via recycling the waste biomass must be promising and beneficial for marine environmental bio-pollution issue and sustainable development considering the large-scale consumption potential for tissue engineering and other applications.

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Fouling sea squirts used as scaffold materials can effectively solve the pollution problem of marine aquaculture.

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The natural electrical conductivity of the sea squirts derived scaffold is similar to that of natural myocardial tissue.

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Cellulose scaffold from sea squirts has a good orientation, and its structure is similar to natural myocardial tissue.

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Sea squirts cellulose derived natural self-conductive scaffolds were successfully served as the functional cardiac patches.

Opisthobranch grazing results in mobilisation of spherulous cells and re-allocation of secondary metabolites in the sponge Aplysina aerophoba

Sponges thrive in marine benthic communities due to their specific and diverse chemical arsenal against predators and competitors. Yet, some animals specifically overcome these defences and use sponges as food and home. Most research on sponge chemical ecology has characterised crude extracts and investigated defences against generalist predators like fish. Consequently, we know little about chemical dynamics in the tissue and responses to specialist grazers. Here, we studied the response of the sponge Aplysina aerophoba to grazing by the opisthobranch Tylodina perversa, in comparison to mechanical damage, at the cellular (via microscopy) and chemical level (via matrix-assisted laser desorption/ionization imaging mass spectrometry, MALDI-imaging MS). We characterised the distribution of two major brominated alkaloids in A. aerophoba, aerophobin-2 and aeroplysinin-1, and identified a generalised wounding response that was similar in both wounding treatments: (i) brominated compound-carrying cells (spherulous cells) accumulated at the wound and (ii) secondary metabolites reallocated to the sponge surface. Upon mechanical damage, the wound turned dark due to oxidised compounds, causing T. perversa deterrence. During grazing, T. perversa's way of feeding prevented oxidation. Thus, the sponge has not evolved a specific response to this specialist predator, but rather relies on rapid regeneration and flexible allocation of constitutive defences.

New Ecological Role of Seaweed Secondary Metabolites as Autotoxic and Allelopathic

Allelopathy and autotoxicity are well-known biological processes in angiosperms but are very little explored or even unknown in seaweeds. In this study, extract and major pure compounds from two distinct populations of the red seaweed Laurencia dendroidea were investigated to evaluate the effect of autotoxicity through auto- and crossed experiments under laboratory conditions, using chlorophyll fluorescence imaging to measure inhibition of photosynthesis (Φ_PSII) as a variable response. Individuals of L. dendroidea from Azeda beach were inhibited by their own extract (IC₅₀ = 219 μg/ml) and the major compound elatol (IC₅₀ = 87 μg/ml); both chemicals also inhibited this seaweed species from Forno beach (IC₅₀ = 194 μg/ml for the extract and IC₅₀ = 277 μg/ml for elatol). By contrast, the extract of L. dendroidea from Forno and its major compound obtusol showed no inhibitory effect in individuals of both populations; but obtusol was insoluble to be tested at higher concentrations, which could be active as observed for elatol. The Azeda population displayed higher susceptibility to the Azeda extract and to elatol, manifested on the first day, unlike Forno individuals, in which the effect was only detected on the second day; and inhibition of Φ_PSII was more pronounced at apical than basal portions of the thalli of L. dendroidea. This first finding of seaweed autotoxicity and allelopathic effects revealed the potential of the chemistry of secondary metabolites for intra- and inter-populational interactions, and for structuring seaweed populations.

Marine Metabolomics: a Method for Nontargeted Measurement of Metabolites in Seawater by Gas Chromatography-Mass Spectrometry

Nontargeted approaches using metabolomics to analyze metabolites that occur in the oceans is less developed than those for terrestrial and limnic ecosystems. One of the challenges in marine metabolomics is that salt limits metabolite analysis in seawater to methods requiring salt removal. Building on previous sample preparation methods for metabolomics, we developed SeaMet, which overcomes the limitations of salt on metabolite detection. Considering that the oceans contain the largest dissolved organic matter pool on Earth, describing the marine metabolome using nontargeted approaches is critical for understanding the drivers behind element cycles, biotic interactions, ecosystem function, and atmospheric CO₂ storage. Our method complements both targeted marine metabolomic investigations as well as other “omics” (e.g., genomics, transcriptomics, and proteomics) approaches by providing an avenue for studying the chemical interaction between marine microbes and their habitats.

Microbial communities exchange molecules with their environment, which plays a major role in regulating global biogeochemical cycles and climate. While extracellular metabolites are commonly measured in terrestrial and limnic ecosystems, the presence of salt in marine habitats limits the nontargeted analyses of the ocean exometabolome using mass spectrometry (MS). Current methods require salt removal prior to sample measurements, which can alter the molecular composition of the metabolome and limit the types of compounds detected by MS. To overcome these limitations, we developed a gas chromatography MS (GC-MS) method that avoids sample altering during salt removal and that detects metabolites down to nanomolar concentrations from less than 1 ml of seawater. We applied our method (SeaMet) to explore marine metabolomes in vitro and in vivo. First, we measured the production and consumption of metabolites during the culture of a heterotrophic bacterium, Marinobacter adhaerens. Our approach revealed successional uptake of amino acids, while sugars were not consumed. These results show that exocellular metabolomics provides insights into nutrient uptake and energy conservation in marine microorganisms. We also applied SeaMet to explore the in situ metabolome of coral reef and mangrove sediment porewaters. Despite the fact that these ecosystems occur in nutrient-poor waters, we uncovered high concentrations of sugars and fatty acids, compounds predicted to play a key role for the abundant and diverse microbial communities in coral reef and mangrove sediments. Our data demonstrate that SeaMet advances marine metabolomics by enabling a nontargeted and quantitative analysis of marine metabolites, thus providing new insights into nutrient cycles in the oceans.

IMPORTANCE Nontargeted approaches using metabolomics to analyze metabolites that occur in the oceans is less developed than those for terrestrial and limnic ecosystems. One of the challenges in marine metabolomics is that salt limits metabolite analysis in seawater to methods requiring salt removal. Building on previous sample preparation methods for metabolomics, we developed SeaMet, which overcomes the limitations of salt on metabolite detection. Considering that the oceans contain the largest dissolved organic matter pool on Earth, describing the marine metabolome using nontargeted approaches is critical for understanding the drivers behind element cycles, biotic interactions, ecosystem function, and atmospheric CO₂ storage. Our method complements both targeted marine metabolomic investigations as well as other “omics” (e.g., genomics, transcriptomics, and proteomics) approaches by providing an avenue for studying the chemical interaction between marine microbes and their habitats.

The culturable mycobiota associated with the Mediterranean sponges Aplysina cavernicola, Crambe crambe and Phorbas tenacior

Marine fungi are part of the huge and understudied biodiversity hosted in the sea. To broaden the knowledge on fungi inhabiting the Mediterranean Sea and their role in sponge holobiont, three sponges namely Aplysina cavernicola, Crambe crambe and Phorbas tenacior were collected in Villefranche sur Mer, (France) at about 25 m depth. The fungal communities associated with the sponges were isolated using different techniques to increase the numbers of fungi isolated. All fungi were identified to species level giving rise to 19, 13 and 3 species for P. tenacior, A. cavernicola and C. crambe, respectively. Of note, 35.7% and 50.0% of the species detected were either reported for the first time in the marine environment or in association with sponges. The mini-satellite analysis confirmed the uniqueness of the mycobiota of each sponge, leading to think that the sponge, with its metabolome, may shape the microbial community.

Transdifferentiation and mesenchymal-to-epithelial transition during regeneration in Demospongiae (Porifera)

Origin and early evolution of regeneration mechanisms remain among the most pressing questions in animal regeneration biology. Porifera have exceptional regenerative capacities and, as early Metazoan lineage, are a promising model for studying evolutionary aspects of regeneration. Here, we focus on reparative regeneration of the body wall in the Mediterranean demosponge Aplysina cavernicola. The epithelialization of the wound surface is completed within 2 days, and the wound is completely healed within 2 weeks. The regeneration is accompanied with the formation of a mass of undifferentiated cells (blastema), which consists of archaeocytes, dedifferentiated choanocytes, anucleated amoebocytes, and differentiated spherulous cells. The main mechanisms of A. cavernicola regeneration are cell dedifferentiation with active migration and subsequent redifferentiation or transdifferentiation of polypotent cells through the mesenchymal-to-epithelial transformation. The main cell sources of the regeneration are archaeocytes and choanocytes. At early stages of the regeneration, the blastema almost devoid of cell proliferation, but after 24 hr postoperation (hpo) and up to 72 hpo numerous DNA-synthesizing cells appear there. In contrast to intact tissues, where vast majority of DNA-synthesizing cells are choanocytes, all 5-ethynyl-2'-deoxyuridine-labeled cells in the blastema are mesohyl cells. Intact tissues, distant from the wound, retains intact level of cell proliferation during whole regeneration process. For the first time, the apoptosis was studied during the regeneration of sponges. Two waves of apoptosis were detected during A. cavernicola regeneration: The first wave at 6-12 hpo and the second wave at 48-72 hpo.

Long-term experimental in situ farming of Crambe crambe (Demospongiae: Poecilosclerida)

Background

The marine sponge Crambe crambe was chosen as an experimental model of sustainable shallow-water mariculture in the Sardinian Sea (Western Mediterranean) to provide biomass with high potential in applied research.

Methods

Explants were cultured in four long-term experiments (19 and 31 months at ca. 2.5 m depth), to determine the suitability of new culture techniques by testing substrata and seeding time (season), and monitoring survival and growth. Explants were excised and grown in an experimental plant close to the wild donor sponge population. Percentage growth rate (GR%) was measured in terms of surface cover area, and explant survival was monitored in situ by means of a digital photo camera.

Results

Explant survival was high throughout the trial, ranging from 78.57% to 92.85% on travertine tiles and from 50% to 71.42% on oyster shells. A few instances of sponge regression were observed. Explant cover area correlated positively with season on two substrata, i.e., tiles and shells. The surface cover area and GR% of explants were measured in the starting phase and monitored up to the end of the trial. High GR% values were observed both on tiles (>21%) and on oyster shells (>15%).

Discussion

The data on the behaviour and life-style of cultured fragments, together with an increase >2,400% in cover area, demonstrate that in situ aquaculture is a viable and sustainable method for the shallow-water biomass supply of Crambe crambe.

Batzella, Crambe and Monanchora: Highly Prolific Marine Sponge Genera Yielding Compounds with Potential Applications for Cancer and Other Therapeutic Areas

Pyrroloquinoline and guanidine-derived alkaloids present distinct groups of marine secondary metabolites with structural diversity that displayed potentialities in biological research. A considerable number of these molecular architectures had been recorded from marine sponges belonging to different marine genera, including Batzella, Crambe, Monanchora, Clathria, Ptilocaulis and New Caledonian starfishes Fromia monilis and Celerina heffernani. In this review, we aim to comprehensively cover the chemodiversity and the bioactivities landmarks centered around the chemical constituents exclusively isolated from these three marine genera including Batzella, Crambe and Monanchora over the period 1981-2017, paying a special attention to the polycyclic guanidinic compounds and their proposed biomimetic landmarks. It is concluded that these marine sponge genera represent a rich source of novel compounds with potential applications for cancer and other therapeutic areas.

How Environmental Factors Affect the Production of Guanidine Alkaloids by the Mediterranean Sponge Crambe crambe

Most marine sponges are known to produce a large array of low molecular-weight metabolites which have applications in the pharmaceutical industry. The production of so-called specialized metabolites may be closely related to environmental factors. In this context, assessing the contribution of factors like temperature, nutrients or light to the metabolomes of sponges provides relevant insights into their chemical ecology as well as the supply issue of natural sponge products. The sponge Crambe crambe was chosen as a model due to its high content of specialized metabolites belonging to polycyclic guanidine alkaloids (PGA). First results were obtained with field data of both wild and farmed specimens collected in two seasons and geographic areas of the North-Western Mediterranean. Then, further insights into factors responsible for changes in the metabolism were gained with sponges cultivated under controlled conditions in an aquarium. Comparative metabolomics showed a clear influence of the seasons and to a lesser extent of the geography while no effect of depth or farming was observed. Interestingly, sponge farming did not limit the production of PGA, while ex situ experiments did not show significant effects of several abiotic factors on the specialized metabolome at a one-month time scale. Some hypotheses were finally proposed to explain the very limited variations of PGA in C. crambe placed under different environmental conditions.