Molecular systematics of sponges (Porifera)

The first application of molecular systematics to sponges was in the 1980s, using allozyme divergence to dis-criminate between conspecific and congeneric sponge populations. Since this time, a fairly large database has been accumulated and, although the first findings seemed to indicate that sponge species were genetically more divergent than those of other marine invertebrates, a recent review of the available dataset indicates that levels of interspecific gene identities in most sponges fall within the normal range found between species of other invertebrates. Nevertheless, some sponge genera have species that are extremely divergent from each other, suggesting a possible polyphyly of these genera. In the 1990s, molecular studies comparing sequences of ribosomal RNA have been used to reappraise the phylogenetic relationships among sponge genera, families, orders and classes. Both the 18S small subunit and the 28S large subunit rRNA genes have been sequenced (41 complete or partial and 75 partial sequences, respectively). Sequences of 18S rRNA show good support for Porifera being true Metazoa, but they are not informative for resolving relationships among genera, families or orders. 28S rRNA domains D1 and D2 appear to be more informative for the terminal nodes and provide resolution for internal topologies in sufficiently closely related species, but the deep nodes between orders or classes cannot be resolved using this molecule. Recently, a more conserved gene, Hsp70, has been used to try to resolve the relationships in the deep nodes. Metazoan monophyly is very well supported. Nevertheless, the divergence between the three classes of Porifera, as well as the divergence between Porifera, Cnidaria and Ctenophora, is not resolved. Research is in progress using other genes such as those of the homeodomain, the tyrosine kinase domain, and those coding for the aggregation factor. For the moment the dataset for these genes is too restricted to resolve the phylogenetic relationships of these phyla. However, whichever the genes, the phylogenies obtained suggest that Porifera could be paraphyletic and that the phylogenetic relationships of most of the families and orders of the Demospongiae have to be reassessed. The Calcarea and Hexactinellida are still to be studied at the molecular level.     

Assessing the diversity of bacterial communities from marine sponges and their bioactive compounds

Symbiotic bacteria play vital roles in the survival and health of marine sponges. Sponges harbor rich, diverse and species-specific microbial communities. Symbiotic marine bacteria have increasingly been reported as promising source of bioactive compounds. A culturomics-based study was undertaken to study the diversity of bacteria from marine sponges and their antimicrobial potential. We have collected three sponge samples i.e. Acanthaster carteri, Rhytisma fulvum (soft coral) and Haliclona caerulea from north region (Obhur) of Red Sea, Jeddah Saudi Arabia. Total of 144 bacterial strains were isolated from three marine sponges using culture dependent method. Screening of isolated strains showed only 37 (26%) isolates as antagonists against oomycetes pathogens (P. ultimum and P. capsici). Among 37 antagonistic bacteria, only 19 bacterial strains exhibited antibacterial activity against human pathogens (Methicillin-resistant Staphylococcus aureus (MRSA) ATCC 43300, Pseudomonas aeruginosa ATCC 27853, Escherichia coli ATCC 8739, Enterococcus faecalis ATCC 29212). Four major classes of bacteria i.e γ-Proteobacteria, α-Proteobacteria, Firmicutes and Actinobacteria were recorded from three marine sponges where γ-Proteobacteria was dominant class. One potential bacterial strain Halomonas sp. EA423 was selected for identification of bioactive metabolites using GC and LC-MS analyses. Bioactive compounds Sulfamerazine, Metronidazole-OH and Ibuprofen are detected from culture extract of strain Halomonas sp. EA423. Overall, this study gives insight into composition and diversity of antagonistic bacterial community of marine sponges and coral from Red Sea and presence of active metabolites from potential strain. Our results showed that these diverse and potential bacterial communities further need to be studied to exploit their biotechnological significance.     

Spicules of hexactinellid sponges (Hexactinellida: Porifera) as natural composite materials

This paper reviews studies on the hexactinellid glass sponges (Hexactinellida: Porifera) that have organic silica spicules. According to its physical properties (microdensity, Young’s modulus, and light transmission), the material of the spicules is similar to amorphous silica; however, sponge spicules are birefringent, which suggests that they have a highly ordered crystal-like nature. Mineralized remnants of siliceous spicules composed of chemically inert materials are preserved in sedimentary rocks and provide evidence of the ecological state of the ancient biosphere. Sponges occur in waters with low temperatures; therefore, they grow very slowly and live for hundreds of years. The organic silica spicules exhibit the capacity for triboluminescence. The generated light emission may be used by symbiotic bacteria on the spicule surface.     

First evidence of chitin as a component of the skeletal fibers of marine sponges. Part I. Verongidae (demospongia: Porifera)

The Porifera (sponges) are often regarded as the oldest, extant metazoan phylum, also bearing the ancestral stage for most features occurring in higher animals. The absence of chitin in sponges, except for the wall of peculiar resistance bodies produced by a highly derived fresh-water group, is puzzling, since it points out chitin to be an autapomorphy for a particular sponge family rather than the ancestral condition within the metazoan lineage. By investigating the internal proteinaceous (spongin) skeleton of two demosponges (Aplysina sp. and Verongula gigantea) using a wide array of techniques (Fourier transform infrared (FTIR), Raman, X-ray, Calcofluor White Staining, Immunolabeling, and chitinase test), we show that chitin is a component of the outermost layer (cuticle) of the skeletal fibers of these demosponges. FTIR and Raman spectra, as well as X-ray difractograms consistently revealed that sponge chitin is much closer to the alpha-chitin known from other animals than to beta-chitin. These findings support the view that the occurrence of a chitin-producing system is the ancestral condition in Metazoa, and that the alpha-chitin is the primitive form in animals.     

First evidence of the presence of chitin in skeletons of marine sponges. Part II. Glass sponges (Hexactinellida: Porifera)

Sponges (Porifera) are presently gaining increased scientific attention because of their secondary metabolites and specific skeleton structures. In contrast to demosponges, whose skeletons are formed from biopolymer spongin, glass sponges (hexactinellids) possess silica-organic composites as the main natural material for their skeletal fibres. Chitin has a crystalline structure and it constitutes a network of organized fibres. This structure confers rigidity and resistance to organisms that contain it, including monocellular (yeast, amoeba, diatoms) and multicellular (higher fungi, arthropods, nematodes, molluscs) organisms. In contrast to different marine invertebrates whose exoskeletons are built of chitin, this polysaccharide has not been found previously as an endogenous biopolymer within glass sponges (Hexactinellida). We hypothesized that glass sponges, which are considered to be the most basal lineage of multicellular animals, must possess chitin. Here, we present a detailed study of the structural and physico-chemical properties of skeletal fragments of the glass sponge Farrea occa. We show that these fibres have a layered design with specific compositional variations in the chitin/silica composite. We applied an effective approach for the demineralization of glass sponge skeletal formations based on an etching procedure using alkali solutions. The results show unambiguously that alpha-chitin is an essential component of the skeletal structures of Hexactinellida. This is the first report of a silica-chitin's composite biomaterial found in nature. From this perspective, the view that silica-chitin scaffolds may be key templates for skeleton formation also in ancestral unicellular organisms, rather than silica-protein composites, emerges as a viable alternative hypothesis.     

First evidences of surfactant biodegradation by marine sponges (Porifera): an experimental study with a linear alkylbenzenesulfonate

The main objective of this work was to better appreciate the role of benthic macro-organisms in the biodegradation of detergents in the marine environment. Sponges, which could be highly resistant to pollution and which are highly active filter-feeders, appear as interesting organisms in this topic. An experimental study conducted in aquarium with seawater enriched in a pure linear alkylbenzenesulfonate (LAS), namely 1-(p-Sulfophenyl)nonane, has shown that the primary degradation was 10 times more rapid in the presence of the sponge Spongia officinalis than in the presence of only marine bacteria. The main degradation metabolites, 3-(p-sulfophenyl)propionic acid and p-sulfobenzoic acid were produced in greater amounts in the presence of sponge. The very rapid degradation kinetics observed in this study may be due to the symbiotic microbial community present in S. officinalis. The sponge may also have promoted the activity of marine bacteria by transforming the original molecule in a more available secondary product. This study demonstrates for the first time that benthic macro-organisms can play an important role in the transformation of biodegradable contaminants, such as LAS.     

Condensation rhythm of fresh-water sponges (Spongillidae, Porifera)

The mesenchyme continuum of spongillids exhibits rhythmic changes that at first glance appear to be contractions. Actually, however, the process is a condensation initiated by the formation of punctate cell contacts and a rapid swelling of all mesenchymal cells. As the cells come into closer contact and the spaces between them are constricted, the volume of the mesenchyme shrinks, giving the impression of a contraction. It seems likely that rhythmic mesenchyme condensation assists the choanocyte chambers in pumping water through the sponge.     

The sterols of calcareous sponges (Calcarea, Porifera)

Sponges are sessile suspension-feeding organisms whose internal phylogenetic relationships are still the subject of intense debate. Sterols may have the potential to be used as independent markers to test phylogenetic hypotheses. Twenty representative specimens of calcareous sponges (class Calcarea, phylum Porifera) with a broad coverage within both subclasses Calcinea and Calcaronea were analysed for their sterol content. Two major pseudohomologous series were found, accompanied by some additional sterols. The first series encompassing conventional C(27) to C(29)Delta(5,7,22) sterols represented the major sterols, with ergosterol (ergosta-5,7,22-trien-3beta-ol, C(28)Delta(5,7,22)) being most prominent in many species. The second series consisted of unusual C(27) to C(29)Delta(5,7,9(11),22) sterols. Cholesterol occurred sporadically, mostly in trace amounts. The sterol patterns did not resolve intraclass phylogenetic relationships, namely the distinction between the subclasses, Calcinea and Calcaronea. This pointed towards major calcarean lipid traits being established prior to the separation of subclasses. Furthermore, calcarean sterol patterns clearly differ from those found in Hexactinellida, whereas partial overlap occurred with some Demospongiae. Hence, sterols only partly reflect the phylogenetic separation of Calcarea from both of the other poriferan classes that was proposed by recent molecular work and fatty acid analyses.     

First report on chitinous holdfast in sponges (Porifera)

A holdfast is a root- or basal plate-like structure of principal importance that anchors aquatic sessile organisms, including sponges, to hard substrates. There is to date little information about the nature and origin of sponges’ holdfasts in both marine and freshwater environments. This work, to our knowledge, demonstrates for the first time that chitin is an important structural component within holdfasts of the endemic freshwater demosponge Lubomirskia baicalensis. Using a variety of techniques (near-edge X-ray absorption fine structure, Raman, electrospray ionization mas spectrometry, Morgan–Elson assay and Calcofluor White staining), we show that chitin from the sponge holdfast is much closer to α-chitin than to β-chitin. Most of the three-dimensional fibrous skeleton of this sponge consists of spicule-containing proteinaceous spongin. Intriguingly, the chitinous holdfast is not spongin-based, and is ontogenetically the oldest part of the sponge body. Sequencing revealed the presence of four previously undescribed genes encoding chitin synthases in the L. baicalensis sponge. This discovery of chitin within freshwater sponge holdfasts highlights the novel and specific functions of this biopolymer within these ancient sessile invertebrates.     

Glass sponges (Porifera, Hexactinellida) of the northern Mid-Atlantic Ridge

Glass sponges (Hexactinellida) collected under the framework of the MAR-ECO project on the G.O. Sars cruise to the northern Mid-Atlantic Ridge, between the Azores and the Reykjanes Ridge, and on the 49th cruise of Akademik Mstislav Keldysh to the Charlie-Gibbs Fracture Zone are described. Fourteen species were identified in the material. This relatively rich fauna includes several novel findings, indicating that the hexactinellid fauna of the northern Mid-Atlantic Ridge is poorly investigated. One genus, Dictyaulus, has never before been reported from the Atlantic Ocean. Two species belonging to the genera Heterotella and Amphidiscella are new to science. Two other species, Rossella nodastrella Topsent, 1915 and Doconestes sessilis Topsent, 1928, have been collected just one other time. Finally, a probable new genus of Euplectellidae, which unfortunately cannot be adequately described because of how small the specimens are, is represented among these collections. A large portion of dead, rigid skeletons of Euretidae and spicule mats of Rossellidae are also reported but not described in detail. Representation of some genera in the Charlie-Gibbs Fracture Zone, coupled with recent observations from elsewhere along the Mid-Atlantic mountain chain, suggests that this fauna is as similar to those of the Indian Ocean and Indo-West Pacific as it is to West or East Atlantic faunas.     

Photosynthetic marine organisms as a source of anticancer compounds

Since early human history, plants have served as the most important source of medicinal natural products, and even in the “synthetic age” the majority of lead compounds for pharmaceutical development remain of plant origin. In the marine realm, algae and seagrasses were amongst the first organisms investigated by marine natural products scientists on their quest for novel pharmaceutical compounds. Forty years after the pioneering work in the field of marine drug discovery began, the biodiversity of marine organisms investigated as potential sources of anticancer, anti-inflammatory, and antibiotic compounds has increased tremendously. Nonetheless, marine plants are still an important source of novel secondary metabolites with interesting biomedical properties. The present review focuses on the antitumour properties of compounds isolated from marine algae, phytoplankton, mangroves, seagrasses, or cordgrasses. Compounds produced by marine epi- or endophytic fungi are also discussed.     

Lichens as a potential natural source of bioactive compounds: a review

Biological activity of material whether known in folk medicine or observed in planned screening program has been the starting point in the drug research. The general pattern is the isolation of active principles, elucidation their structures, followed by attempts for modulation of its activity potential by chemical modification. Lichens are valuable plant resources and are used as medicine, food, fodder, perfume, spice, dyes and for miscellaneous purposes throughout the world. Lichens are well known for the diversity of secondary metabolites that they produce. Compounds isolated from various lichen species have been reported to display diverse biological activities. Here we review the medicinal efficacy of lichen substances, which intends to explore the pharmaceutical potential of lichen substances.     

The fatty acids of calcareous sponges (Calcarea, Porifera)

Twenty-nine specimens of calcareous sponges (Class Calcarea, Phylum Porifera), covering thirteen representative species of the families Soleneiscidae, Leucaltidae, Levinellidae, Leucettidae, Clathrinidae, Sycettidae, Grantiidae, Jenkinidae, and Heteropiidae were analysed for their fatty acids. The fatty acids of Calcarea generally comprise saturated and monounsaturated linear (n-), and terminally methylated (iso-, anteiso-) C(14)-C(20) homologues. Furthermore, polyunsaturated C(22) fatty acids and the isoprenoic 4,8,12-trimethyltridecanoic acid were found. The most prominent compounds are n-C(16), iso-C(17), iso-C(18), n-C(18), n-C(20). In addition, a high abundance of the exotic 16-methyloctadecanoic acid (anteiso-C(19)) appears to be a characteristic trait of Calcarea. Long-chain 'demospongic acids', typically found in Demospongiae and Hexactinellida, are absent in Calcarea. The completely different strategy of calcarean fatty acid synthesis supports their phylogenetic distinctiveness from a common Demospongiae/Hexactinellida taxon. Both intraspecific and intraclass patterns of Calcarea showed great similarity, suggesting a conserved fatty acid composition that already existed in the last common ancestor of Calcinea and Calcaronea, i.e. before subclasses diverged.     

First evidence of miniature transposable elements in sponges (Porifera)

Transposable elements play a vital role in genome evolution and may have been important for the formation of the early metazoan genome, but only little is known about transposons at this interface between unicellular opisthokonts and Metazoa. Here, we describe the first miniature transposable elements (MITEs, Queen1 and Queen2) in sponges. Queen1 and Queen2 are probably derived from Tc1/mariner-like MITE families and are represented in more than 3,800 and 1,700 copies, respectively, in the Amphimedon queenslandica genome. Queen elements are located in intergenic regions as well as in introns, providing the potential to induce new splicing sites and termination signals in the genes. Further possible impacts of MITEs on the evolution of the metazoan genome are discussed.     

Inferring the ancestral sexuality and reproductive condition in sponges (Porifera)

Considerable diversity abounds among sponges with respect to reproductive and developmental biology. Their ancestral sexual mode (gonochorism vs. hermaphroditism) and reproductive condition (oviparity vs. viviparity) however remain unclear, and these traits appear to have undergone correlated evolution in the phylum. To infer ancestral traits and investigate this putative correlation, we used DNA sequence data from two loci (18S ribosomal RNA and cytochrome c oxidase subunit I) to explore the phylogenetic relationships of 62 sponges whose reproductive traits have been previously documented. Although the inferred tree topologies, using the limited data available, favoured paraphyly of sponges, we also investigated ancestral character‐state reconstruction on a phylogeny with constrained sponge monophyly. Both parsimony‐ and likelihood‐based ancestral state reconstructions indicate that viviparity (brooding) was the likely reproductive mode of the ancestral sponge. Hermaphroditism is favoured over gonochorism as the sexual condition of the sponge ancestor under parsimony, but the reconstruction is ambiguous under likelihood, rendering the ancestry of sexuality unresolved in our study. These results are insensitive to the constraint of sponge monophyly when tracing the reproductive characters using parsimony methods. However, the maximum likelihood analysis of the monophyletic hypothetical tree rendered gonochorism as ancestral for the phylum. A test of trait correlation unambiguously favours the concerted evolution of sexuality and reproductive mode in sponges (hermaphroditism/viviparity, gonochorism/oviparity). Although testing ecological hypotheses for the pattern of sponge reproduction is beyond the scope of our analyses, we postulate that certain physiological constrains might be key causes for the correlation of reproductive characters.     

Marine microorganisms as an untapped source of bioactive compounds

The search for novel biologically active molecules has extended to the screening of organisms associated with less explored environments. In this sense, Oceans, which cover nearly the 67% of the globe, are interesting ecosystems characterized by a high biodiversity that is worth being explored. As such, marine microorganisms are highly interesting as promising sources of new bioactive compounds of potential value to humans. Some of these microorganisms are able to survive in extreme marine environments and, as a result, they produce complex molecules with unique biological interesting properties for a wide variety of industrial and biotechnological applications. Thus, different marine microorganisms (fungi, myxomycetes, bacteria, and microalgae) producing compounds with antioxidant, antibacterial, apoptotic, antitumoral and antiviral activities have been already isolated. This review compiles and discusses the discovery of bioactive molecules from marine microorganisms reported from 2018 onwards. Moreover, it highlights the huge potential of marine microorganisms for obtaining highly valuable bioactive compounds.