Variations of antioxidant efficiency and presence of endosymbiotic diatoms in the Antarctic porifera Haliclona dancoi

Chemical and microbiological insights into two littoral Antarctic demosponge species: Haliclona (Rhizoniera) dancoi (Topsent 1901) and Haliclona (Rhizoniera) scotti (Kirkpatrick 1907)

Introduction

Antarctic Porifera have gained increasing interest as hosts of diversified associated microbial communities that could provide interesting insights on the holobiome system and its relation with environmental parameters.

Methods

The Antarctic demosponge species Haliclona dancoi and Haliclona scotti were targeted for the determination of persistent organic pollutant (i. e., polychlorobiphenyls, PCBs, and polycyclic aromatic hydrocarbons, PAHs) and trace metal concentrations, along with the characterization of the associated prokaryotic communities by the 16S rRNA next generation sequencing, to evaluate possible relationships between pollutant accumulation (e.g., as a stress factor) and prokaryotic community composition in Antarctic sponges. To the best of our knowledge, this approach has been never applied before.

Results

Notably, both chemical and microbiological data on H. scotti (a quite rare species in the Ross Sea) are here reported for the first time, as well as the determination of PAHs in Antarctic Porifera. Both sponge species generally contained higher amounts of pollutants than the surrounding sediment and seawater, thus demonstrating their accumulation capability. The structure of the associated prokaryotic communities, even if differing at order and genus levels between the two sponge species, was dominated by Proteobacteria and Bacteroidota (with Archaea abundances that were negligible) and appeared in sharp contrast to communities inhabiting the bulk environment.

Discussions

Results suggested that some bacterial groups associated with H. dancoi and H. scotti were significantly (positively or negatively) correlated to the occurrence of certain contaminants.

The Porifera microeukaryome: Addressing the neglected associations between sponges and protists

While bacterial and archaeal communities of sponges are intensively studied, given their importance to the animal's physiology as well as sources of several new bioactive molecules, the potential and roles of associated protists remain poorly known. Historically, culture-dependent approaches dominated the investigations of sponge-protist interactions. With the advances in omics techniques, these associations could be visualized at other equally important scales. Of the few existing studies, there is a strong tendency to focus on interactions with photosynthesizing taxa such as dinoflagellates and diatoms, with fewer works dissecting the interactions with other less common groups. In addition, there are bottlenecks and inherent biases in using primer pairs and bioinformatics approaches in the most commonly used metabarcoding studies. Thus, this review addresses the issues underlying this association, using the term "microeukaryome" to refer exclusively to protists associated with an animal host. We aim to highlight the diversity and community composition of protists associated with sponges and place them on the same level as other microorganisms already well studied in this context. Among other shortcomings, it could be observed that the biotechnological potential of the microeukaryome is still largely unexplored, possibly being a valuable source of new pharmacological compounds, enzymes and metabolic processes.

Effects of sponge-derived Ageladine A on the photosynthesis of different microalgal species and strains

Fluorescent natural compounds have been identified in several marine hosts of microalgae. Their prevalence, and the energy the host is expending on their synthesis, suggests an important, yet poorly understood ecological role. It has been suggested that some of these natural products may enhance the photosynthesis of microbial symbionts. In this study, the effect of Ageladine A (Ag A), a pH-dependent fluorophore found in sponges of the genus Agelas, on the photosynthesis of nine microalgal species and strains was examined. The data showed that the variety of effects of Ag A additions differed between species, and even strains within a species. While in one strain of Synechococcus sp., the presence of Ag A increased gross photosynthesis under UV light exposure, it decreased in another. And while in the chlorophyte T. chuii overall metabolic activity was greatly reduced under all forms of lighting, photosynthesis in T. lutea was positively affected by the addition of Ag A. The variety of effects of Ag A on photosynthesis observed in this study indicate a complex interaction of Ag A with microalgal cells and suggests that a host may be able to shape its own symbiotic microbiome with self-produced natural products.

Sponge-derived Ageladine A affects the in vivo fluorescence emission spectra of microalgae

In several marine hosts of microalgae, fluorescent natural products may play an important role. While the ecological function of these compounds is not well understood, an interaction of these molecules with the photosynthesis of the symbionts has been suggested. In this study, the effect of Ageladine A (Ag A), a pH-dependent fluorophore found in sponges of the genus Agelas, on microalgal fluorescence was examined. The spectra showed an accumulation of Ag A within the cells, but with variable impacts on fluorescence. While in two Synechococcus strains, fluorescence of phycoerythrin increased significantly, the fluorescence of other Synechococcus strains was not affected. In four out of the five eukaryote species examined, chlorophyll a (Chl a) fluorescence intensity was modulated. In Tisochrysis lutea, for example, the position of the fluorescence emission maximum of Chl a was shifted. The variety of these effects of Ag A on microalgal fluorescence suggests that fluorophores derived from animals could play a crucial role in shaping the composition of marine host/symbiont systems.

Recycling resources: silica of diatom frustules as a source for spicule building in Antarctic siliceous demosponges

Dissolved silicon (DSi) is biologically processed to produce siliceous skeletons by a variety of organisms including radiolarians, silicoflagellates, choanoflagellates, plants, diatoms and some animals. In the photic ocean, diatoms are dominant consumers over competing other silicifiers. In Antarctica, where DSi is not particularly limiting, diatoms and sponges coexist in high abundances. Interestingly, diatom ingestion by sponges is a regular feeding strategy there. Although it was known that the diatom organic nutrients are readily metabolized by the sponges, what happened to the inorganic diatom silica skeleton remained unexplored. Here, we have conducted a multi-analytical approach to investigate the processing of diatom silica and whether it is reconverted into sponge silica. We have documented widespread diatom consumption by several demosponges, identifying storage vesicles for the diatom-derived silica by electron microscopy and microanalysis. Diatom-consuming sponges showed upregulation of silicatein and silicase genes, which in addition to the δ 30Si values of their silica, supports that the sponges are converting the ingested diatom silica into sponge silica without much further Si fractionation. Our multidisciplinary approach suggests that the reutilization of diatom silica by sponges is a common feature among Antarctic sponges, which should be further investigated in other latitudes and in other silicifiers.

Biotechnological Applications of Bioactive Peptides From Marine Sources

This review is an overview on marine bioactive peptides with promising activities for the development of alternative drugs to fight human pathologies. In particular, we focus on potentially prolific producers of peptides in microorganisms, including sponge-associated bacteria and marine photoautotrophs such as microalgae and cyanobacteria. Microorganisms are still poorly explored for drug discovery, even if they are highly metabolically plastic and potentially amenable to culturing. This offers the possibility of obtaining a continuous source of bioactive compounds to satisfy the challenging demands of pharmaceutical industries. This review targets peptides because of the variety of potent biological activities demonstrated by these molecules, including antiviral, antimicrobial, antifungal, antioxidant, anticoagulant, antihypertensive, anticancer, antidiabetic, antiobesity, and calcium-binding bioactivities. Several of these peptides have already gained recognition as effective drug agents in recent years. We also focus on cutting-edge omic approaches for the discovery of novel compounds for pharmacological applications. With rapid depletion of natural resources, omic technologies may be the solution to efficiently produce a vast variety of novel peptides with unique pharmacological potential.

Silica-induced fibrosis: an ancient response from the early metazoans

Exposure to crystalline silica particles causes silicosis, an occupational disease leading to an overproduction of collagen in the lung. The first step of this pathology is characterized by the release of inflammatory mediators. Tumour necrosis factor (TNF) is a pro-inflammatory cytokine directly involved in silica-induced pulmonary fibrosis. The marine demosponge Chondrosia reniformis is able to incorporate silica grains and partially dissolve the crystalline forms apparently without toxic effects. In the present work, C. reniformis tissue explants were treated with fine quartz dust and the expression level of fibrogenic genes was assayed by qPCR, demonstrating an overexpression of a fibrillar and a non-fibrillar collagen and of prolyl-4-hydroxylase enzyme. The deposition of new collagen could also be documented in quartz-treated sponge explants. Furthermore, TNF pro-inflammatory cytokine overexpression and involvement in silica-induced sponge collagen biosynthesis was demonstrated in quartz-treated explants as compared with controls by means of specific TNF inhibitors affecting the fibrogenic gene response. As no documentable detrimental effect was observed in treated explants, we conclude that the C. reniformis unique quartz engulfment and erosion is physiological and beneficial to the animal, leading to new collagen synthesis and strengthening of the body stiffness. Thus, we put forward the hypothesis that an ancient physiological behaviour from the lowest of the Metazoa, persisting through evolution via the same molecular mediators such as TNF, may have become the cause of disease in the specialized tissues of higher animals such as mammals.

Activity of Haliscosamine against Fusarium oxysporum f.sp. melonis: in vitro and in vivo analysis

Marine sponges are a potential source of new molecules with diverse biological activities. We have previously isolated a sphingosine derivative, (9Z)-2-amino-docos-9-ene-1,3,13,14-tetraol (Haliscosamine) from the Moroccan sea sponge Haliclona viscosa. The aim of this study was to test Haliscosamine in vitro and in vivo for its antifungal activity against Fusarium oxysporum f.sp. melonis causing fusarium wilt of melon.

Overall, in vitro test showed that haliscosamine has a similar effect as DESOGERME SP VEGETAUX®. In addition, in vivo showed a significant effect against Fusarium oxysporum f.sp. melonis. Taking to gather, our results suggest that haliscosamine constitutes a potential candidate against Fusarium oxysporum f.sp. melonis and the possibility to use in phytopathology.

Natural products mediating ecological interactions in Antarctic benthic communities: a mini-review of the known molecules

Out of the many bioactive compounds described from the oceans, only a small fraction have been studied for their ecological significance. Similarly, most chemically mediated interactions are not well understood, because the molecules involved remain unrevealed. In Antarctica, this gap in knowledge is even more acute in comparison to tropical or temperate regions, even though polar organisms are also prolific producers of chemical defenses, and pharmacologically relevant products are being reported from the Southern Ocean. The extreme and unique marine environments surrounding Antarctica along with the numerous unusual interactions taking place in benthic communities are expected to select for novel functional secondary metabolites. There is an urgent need to comprehend the evolutionary role of marine derived substances in general, and particularly at the Poles, since molecules of keystone significance are vital in species survival, and therefore, in structuring the communities. Here we provide a mini-review on the identified marine natural products proven to have an ecological function in Antarctic ecosystems. This report recapitulates some of the bibliography from original Antarctic reviews, and updates the new literature in the field from 2009 to the present.

In vitro screening of antifungal activity of marine sponge extracts against five phytopathogenic fungi

The aim of our research is the screening of extracts of marine sponges for their antifungal activity against phytopathogenic fungi. The in vitro screening of hydroalcoholic and organic extracts of ten marine sponges from Atlantic coast of Morocco against five phytopathogenic fungi (Fusarium oxysporum f.sp. melonis, Fusarium oxysporum f.sp. radicis-lycopersici, Fusarium oxysporum f.sp. ciceris, Botrytis cinerea and Penicillium digitatum) showed that only two sponges (Haliclona viscosa and Cynachirella tarentina) are active against all phytopathogenic fungi studied.

Haliscosamine: a new antifungal sphingosine derivative from the Moroccan marine sponge Haliclona viscosa

In the aim of searching for new antifungal products from marine origin, we have isolated a sphingosine derivative, (9Z)-2-amino-docos-9-ene-1,3,13,14-tetraol (Haliscosamine) from the Moroccan sea sponge Haliclona viscosa using bio-guided (antifungal) HPLC methods. The molecular structure of this compound was elucidated by spectrometric techniques IR, UV, MS and NMR. The isolated metabolite showed a significant antifungal activity against Cryptococcus and Candida species and a weak general toxicity in the brine shrimp lethality test. Further research is needed to study its in vivo activity, as well as to elucidate the mechanism underlying its activity in the hope of a future use in medical mycology.

Placozoa and the evolution of Metazoa and intrasomatic cell differentiation

The multicellular Metazoa evolved from single-celled organisms (Protozoa) and usually - but not necessarily - consist of more cells than Protozoa. In all cases, and thus by definition, Metazoa possess more than one somatic cell type, i.e. they show-in sharp contrast to protists-intrasomatic differentiation. Placozoa have the lowest degree of intrasomatic variation; the number of somatic cell types according to text books is four (but see also Jakob W, Sagasser S, Dellaporta S, Holland P, Kuhn K, and Schierwater B. The Trox-2 Hox/ParaHox gene of Trichoplax (Placozoa) marks an epithelial boundary. Dev Genes Evol 2004;214:170-5). For this and several other reasons Placozoa have been regarded by many as the most basal metazoan phylum. Thus, the morphologically most simply organized metazoan animal, the placozoan Trichoplax adhaerens, resembles a unique model system for cell differentiation studies and also an intriguing model for a prominent "urmetazoon" hypotheses-the placula hypothesis. A basal position of Placozoa would provide answers to several key issues of metazoan-specific inventions (including for example different lines of somatic cell differentiation leading to organ development and axis formation) and would determine a root for unraveling their evolution. However, the phylogenetic relationships at the base of Metazoa are controversial and a basal position of Placozoa is not generally accepted (e.g. Schierwater B, DeSalle R. Can we ever identify the Urmetazoan? Integr Comp Biol 2007;47:670-76; DeSalle R, Schierwater B. An even "newer" animal phylogeny. Bioessays 2008;30:1043-47). Here we review and discuss (i) long-standing morphological evidence for the simple placozoan bauplan resembling an ancestral metazoan stage, (ii) some rapidly changing alternative hypotheses derived from molecular analyses, (iii) the surprising idea that triploblasts (Bilateria) and diploblasts may be sister groups, and (iv) the presence of genes involved in cell differentiation and signaling pathways in the placozoan genome.

Sponge-associated microorganisms: evolution, ecology, and biotechnological potential

Marine sponges often contain diverse and abundant microbial communities, including bacteria, archaea, microalgae, and fungi. In some cases, these microbial associates comprise as much as 40% of the sponge volume and can contribute significantly to host metabolism (e.g., via photosynthesis or nitrogen fixation). We review in detail the diversity of microbes associated with sponges, including extensive 16S rRNA-based phylogenetic analyses which support the previously suggested existence of a sponge-specific microbiota. These analyses provide a suitable vantage point from which to consider the potential evolutionary and ecological ramifications of these widespread, sponge-specific microorganisms. Subsequently, we examine the ecology of sponge-microbe associations, including the establishment and maintenance of these sometimes intimate partnerships, the varied nature of the interactions (ranging from mutualism to host-pathogen relationships), and the broad-scale patterns of symbiont distribution. The ecological and evolutionary importance of sponge-microbe associations is mirrored by their enormous biotechnological potential: marine sponges are among the animal kingdom's most prolific producers of bioactive metabolites, and in at least some cases, the compounds are of microbial rather than sponge origin. We review the status of this important field, outlining the various approaches (e.g., cultivation, cell separation, and metagenomics) which have been employed to access the chemical wealth of sponge-microbe associations.