Assessing the complex sponge microbiota: core,variable and species-specific bacterial communities in marine sponges

Marine sponges are well known for their associations with highly diverse, yet very specific and often highly similar microbiota. The aim of this study was to identify potential bacterial sub-populations in relation to sponge phylogeny and sampling sites and to define the core bacterial community. 16S ribosomal RNA gene amplicon pyrosequencing was applied to 32 sponge species from eight locations around the world''s oceans, thereby generating 2567 operational taxonomic units (OTUs at the 97% sequence similarity level) in total and up to 364 different OTUs per sponge species. The taxonomic richness detected in this study comprised 25 bacterial phyla with Proteobacteria, Chloroflexi and Poribacteria being most diverse in sponges. Among these phyla were nine candidate phyla, six of them found for the first time in sponges. Similarity comparison of bacterial communities revealed no correlation with host phylogeny but a tropical sub-population in that tropical sponges have more similar bacterial communities to each other than to subtropical sponges. A minimal core bacterial community consisting of very few OTUs (97%, 95% and 90%) was found. These microbes have a global distribution and are probably acquired via environmental transmission. In contrast, a large species-specific bacterial community was detected, which is represented by OTUs present in only a single sponge species. The species-specific bacterial community is probably mainly vertically transmitted. It is proposed that different sponges contain different bacterial species, however, these bacteria are still closely related to each other explaining the observed similarity of bacterial communities in sponges in this and previous studies. This global analysis represents the most comprehensive study of bacterial symbionts in sponges to date and provides novel insights into the complex structure of these unique associations.     

Eocene siliceous sponges from the Ebro Basin (Catalonia, Spain)

The Eocene (Bartonian) marls of the La Guixa Member and Gurb Member, Vic Marls Formation (Ebro Basin, Catalonia, Spain), contain a very rich and diversified siliceous sponge fauna. The fauna is dominated by hexactinellids; lithistids and other demosponges are rare. It consists of 16 species representing 16 genera. Eleven new species and two new genera are proposed for these sponges: Reguantella cavernosa nov. gen. nov. sp., Regadrella concinna nov. sp. (both Hexactinellida, Lyssacinosa), Eurete clava nov. sp., Pleuroguettardia iberica nov. sp., Aphrocallistes almeriae nov. sp., Hexactinella informis nov. sp. (all Hexactinellida, Hexactinosa), Brachiolites munterensis nov. sp., Centrosia viquensis nov. sp., Callicylix eocenicus nov. sp., Rhizocheton robustus nov. sp. (all Hexactinellida, Lychniscosa), Propetrosia pristina nov. gen. nov. sp. (Demospongia, Haplosclerida). Some genera of sponges in this fauna are still extant, but, in general, the predominant ones are very close in morphology, and, without doubt, closely related to the Late Cretaceous sponges. This fauna also differs considerably, in terms of composition, from most other described faunas of Tertiary sponges from the Mediterranean region, which are dominated by lithistid sponges. Lithistid sponges are rare in this investigated assemblage, which seems most similar to an as yet undescribed Eocene fauna from Italy. There is ecological differentiation in the proportions of particular sponges in various outcrops and/or stratigraphical levels that is clearly associated with water-depth-related controlling factor(s): Munter, Tona and Sta. Cecilia represent the deepest facies, Gurb is intermediate, and St. Roc and Vespella are the most shallow. The exact bathymetric position of the sponge fauna is difficult to estimate, but it seems that 100 m (but probably 200 m and more in the case of the deepest parts) of water depth may be inferred for this facies.     

Changes in Bacterial Communities of the Marine Sponge Mycale laxissima on Transfer into Aquaculture

The changes in bacterial communities associated with the marine sponge Mycale laxissima on transfer to aquaculture were studied using culture-based and molecular techniques. M. laxissima was maintained alive in flowthrough and closed recirculating aquaculture systems for 2 years and 1 year, respectively. The bacterial communities associated with wild and aquacultured sponges, as well as the surrounding water, were assessed using 16S rRNA gene clone library analysis and denaturing gradient gel electrophoresis (DGGE). Bacterial richness and diversity were measured using DOTUR computer software, and clone libraries were compared using S-LIBSHUFF. DGGE analysis revealed that the diversity of the bacterial community of M. laxissima increased when sponges were maintained in aquaculture and that bacterial communities associated with wild and aquacultured M. laxissima were markedly different than those of the corresponding surrounding water. Clone libraries of bacterial 16S rRNA from sponges confirmed that the bacterial communities changed during aquaculture. These communities were significantly different than those of seawater and aquarium water. The diversity of bacterial communities associated with M. laxissima increased significantly in aquaculture. Our work shows that it is important to monitor changes in bacterial communities when examining the feasibility of growing sponges in aquaculture systems because these communities may change. This could have implications for the health of sponges or for the production of bioactive compounds by sponges in cases where these compounds are produced by symbiotic bacteria rather than by the sponges themselves.     

The Different Potential of Sponge Bacterial Symbionts in N2 Release Indicated by the Phylogenetic Diversity and Abundance Analyses of Denitrification Genes,nirK and nosZ

Nitrogen cycle is a critical biogeochemical process of the oceans. The nitrogen fixation by sponge cyanobacteria was early observed. Until recently, sponges were found to be able to release nitrogen gas. However the gene-level evidence for the role of bacterial symbionts from different species sponges in nitrogen gas release is limited. And meanwhile, the quanitative analysis of nitrogen cycle-related genes of sponge microbial symbionts is relatively lacking. The nirK gene encoding nitrite reductase which catalyzes soluble nitrite into gas NO and nosZ gene encoding nitrous oxide reductase which catalyzes N₂O into N₂ are two key functional genes in the complete denitrification pathway. In this study, using nirK and nosZ genes as markers, the potential of bacterial symbionts in six species of sponges in the release of N₂ was investigated by phylogenetic analysis and real-time qPCR. As a result, totally, 2 OTUs of nirK and 5 OTUs of nosZ genes were detected by gene library-based saturated sequencing. Difference phylogenetic diversity of nirK and nosZ genes were observed at OTU level in sponges. Meanwhile, real-time qPCR analysis showed that Xestospongia testudinaria had the highest abundance of nosZ gene, while Cinachyrella sp. had the greatest abundance of nirK gene. Phylogenetic analysis showed that the nirK and nosZ genes were probably of Alpha-, Beta-, and Gammaproteobacteria origin. The results from this study suggest that the denitrification potential of bacteria varies among sponges because of the different phylogenetic diversity and relative abundance of nosZ and nirK genes in sponges. Totally, both the qualitative and quantitative analyses of nirK and nosZ genes indicated the different potential of sponge bacterial symbionts in the release of nitrogen gas.     

Comparative sequence analysis of bacterial symbionts from the marine sponges Geodia cydonium and Ircinia muscarum

Marine sponges (Porifera) live in a symbiotic relationship with microorganisms, primarily bacteria. Recently, several studies indicated that sponges are the most prolific source of biologically-active compounds produced by symbiotic microorganisms rather than by the sponges themselves. In the present study we characterized the bacterial symbionts from two Demospongiae, Ircinia muscarum and Geodia cydonium. We amplified 16S rRNA by PCR, using specific bacterial-primers. The phylogenetic analysis revealed the presence of nine bacterial clones from I. muscarum and ten from G. cydonium. In particular, I. muscarum resulted enriched in Bacillus species and G. cydonium in Proteobacterium species. Since these bacteria were able to produce secondary metabolites with potential biotechnological and biopharmaceutical applications, we hypothesized that I. muscarum and G. cydonium could be a considered as a “gold mine” of natural products.     

Fossilien aus Riffkomplexen der alpinen Trias:Cheilosporites Wähner,eine Foraminifere?

The genusCheilosporites Wähner, a problematicum variously referred to algae and sponges, is widespread in Rhaetian reefs of the Alpine region. Its arborescent colonies are composed of uniserial but branching rows of chambers, penetrated by an axial siphon. The chambers enlarge distally, and undergo marked changes in shape. These characters are to be found neither among algae nor sponges, but are characteristic of many Foraminifera. Despite its relatively large size (chamber diameter up to 4 mm, height of colony probably 5 cm)Cheilosporites is here tentatively referred to the Fortminifera, as only known representative of the new familiy Cheilosporitidae.     

Genomic Mining for Novel FADH2-Dependent Halogenases in Marine Sponge-Associated Microbial Consortia

Many marine sponges (Porifera) are known to contain large amounts of phylogenetically diverse microorganisms. Sponges are also known for their large arsenal of natural products, many of which are halogenated. In this study, 36 different FADH₂-dependent halogenase gene fragments were amplified from various Caribbean and Mediterranean sponges using newly designed degenerate PCR primers. Four unique halogenase-positive fosmid clones, all containing the highly conserved amino acid motif “GxGxxG”, were identified in the microbial metagenome of Aplysina aerophoba. Sequence analysis of one halogenase-bearing fosmid revealed notably two open reading frames with high homologies to efflux and multidrug resistance proteins. Single cell genomic analysis allowed for a taxonomic assignment of the halogenase genes to specific symbiotic lineages. Specifically, the halogenase cluster S1 is predicted to be produced by a deltaproteobacterial symbiont and halogenase cluster S2 by a poribacterial sponge symbiont. An additional halogenase gene is possibly produced by an actinobacterial symbiont of marine sponges. The identification of three novel, phylogenetically, and possibly also functionally distinct halogenase gene clusters indicates that the microbial consortia of sponges are a valuable resource for novel enzymes involved in halogenation reactions.     

Biodiversity of Actinomycetes Associated with Caribbean Sponges and Their Potential for Natural Product Discovery

Marine actinomycetes provide a rich source of structurally unique and bioactive secondary metabolites. Numerous genera of marine actinomycetes have been isolated from marine sediments as well as several sponge species. In this study, 16 different species of Caribbean sponges were collected from four different locations in the coastal waters off Puerto Rico in order to examine diversity and bioactive metabolite production of marine actinomycetes in Caribbean sponges. Sediments were also collected from each location, in order to compare actinomycete communities between these two types of samples. A total of 180 actinomycetes were isolated and identified based on 16S rRNA gene analysis. Phylogenetic analysis revealed the presence of at least 14 new phylotypes belonging to the genera Micromonospora, Verruscosispora, Streptomyces, Salinospora, Solwaraspora, Microbacterium and Cellulosimicrobium. Seventy-eight of the isolates (19 from sediments and 59 from sponges) shared 100 % sequence identity with Micromonospora sp. R1. Despite having identical 16S rRNA sequences, the bioactivity of extracts and subsequent fractions generated from the fermentation of both sponge- and sediment-derived isolates identical to Micromonospora sp. R1 varied greatly, with a marked increase in antibiotic metabolite production in those isolates derived from sponges. These results indicate that the chemical profiles of isolates with high 16S rRNA sequence homology to known strains can be diverse and dependent on the source of isolation. In addition, seven previously reported dihydroquinones produced by five different Streptomyces strains have been purified and characterized from one Streptomyces sp. strain isolated in this study from the Caribbean sponge Agelas sceptrum.     

Environmental shaping of sponge associated archaeal communities

Background

Archaea are ubiquitous symbionts of marine sponges but their ecological roles and the influence of environmental factors on these associations are still poorly understood.

Methodology/Principal Findings

We compared the diversity and composition of archaea associated with seawater and with the sponges Hymeniacidon heliophila, Paraleucilla magna and Petromica citrina in two distinct environments: Guanabara Bay, a highly impacted estuary in Rio de Janeiro, Brazil, and the nearby Cagarras Archipelago. For this we used metagenomic analyses of 16S rRNA and ammonia monooxygenase (amoA) gene libraries. Hymeniacidon heliophila was more abundant inside the bay, while P. magna was more abundant outside and P. citrina was only recorded at the Cagarras Archipelago. Principal Component Analysis plots (PCA) generated using pairwise unweighted UniFrac distances showed that the archaeal community structure of inner bay seawater and sponges was different from that of coastal Cagarras Archipelago. Rarefaction analyses showed that inner bay archaeaoplankton were more diverse than those from the Cagarras Archipelago. Only members of Crenarchaeota were found in sponge libraries, while in seawater both Crenarchaeota and Euryarchaeota were observed. Although most amoA archaeal genes detected in this study seem to be novel, some clones were affiliated to known ammonia oxidizers such as Nitrosopumilus maritimus and Cenarchaeum symbiosum.

Conclusion/Significance

The composition and diversity of archaeal communities associated with pollution-tolerant sponge species can change in a range of few kilometers, probably influenced by eutrophication. The presence of archaeal amoA genes in Porifera suggests that Archaea are involved in the nitrogen cycle within the sponge holobiont, possibly increasing its resistance to anthropogenic impacts. The higher diversity of Crenarchaeota in the polluted area suggests that some marine sponges are able to change the composition of their associated archaeal communities, thereby improving their fitness in impacted environments.     

Relative importance of bacteria, microalgae and yeast for growth of the sponge Halichondria melanadocia (De Laubenfels, 1936): A laboratory study

Bacteria, microalgae and yeast less than 10 μm in size are the primary food source of sponges but their relative contribution to somatic growth is poorly understood. In a laboratory study, the sponge Halichondria melanadocia was fed for 6 weeks a diet consisting solely of four bacterial strains, or a mixed diet consisting of bacteria, microalgae and yeast. Both diets were fed at three concentrations, based on the natural concentration (NC) of particles available to sponges: 1/5, 1 and 5NC. Mean final size of H. melanadocia was 40% greater on a mixed diet than on the bacteria diet, probably because of the greater supply of carbon and other essential nutrients in microalgae and yeast. Cell concentration also significantly affected the growth of H. melanadocia, with greatest growth for sponges fed at the highest cell concentration. The estimated carbon requirement for H. melanadocia to meet metabolic costs was 0.356 mg C l^− 1 or 103 μg C h^− 1 gDW^− 1. Many H. melanadocia appeared to be optimizing their surface area for food uptake.     

Benthic-pelagic coupling on coral reefs: Feeding and growth of Caribbean sponges

Benthic-pelagic coupling and the role of bottom-up versus top-down processes are recognized as having a major impact on the community structure of intertidal and shallow subtidal marine communities. Bottom-up processes, however, are still viewed as principally affecting the outcome of top-down processes. Sponges on coral reefs are important members of the benthic community and provide a crucial coupling between water-column productivity and the benthos. Other than scleractinian corals, sponges dominate many of these habitats where water column productivity is composed of mostly autotrophic and heterotrophic picoplankton that sponges actively filter. While predation upon sponges by invertebrates, fish, and turtles occurs, the sponges Callyspongia vaginalis, Agelas conifera, and Aplysina fistularis from Florida, Belize, and the Bahamas, respectively, exhibit a consistent and significant pattern of greater biomass, rates of growth, and feeding, as does their food supply, with increasing depth. Sponges consume 65-93% of the available particulate food supply and, at all sites, sponges increase in size and growth rate as depth increases, suggesting that food supply and, therefore, bottom-up processes significantly influence the distribution and abundance of sponges in these habitats.     

Chemical profile of adults and buds of the chemically defended marine sponge Tethya maza

Several adults and the corresponding larvae of marine sponges are known as rich sources of secondary metabolites. In this paper we will show the chemical profile of adults and buds of the sponge Tethya maza. Cholesterol, ergost-5,22-dienol-3, stigmast-5,24-dienol-3, cholest-5,22-dienol-3, cholest-5-enol-3-one-7, and stigmast-5,24(28)-dien-3-ol were the major compounds detected, two of them being detected only in crude extracts of the adults while one was present only in the buds. Due to this high similarity it is supposed that buds could be chemically protected with regards to predation as well as the adult individuals of T. maza. This is the first report of chemicals present in the structures (buds) of sponges produced by asexual reproduction.     

Trophic ecology of a freshwater sponge (Spongilla lacustris) revealed by stable isotope analysis

The vital roles that sponges play in marine habitats are well-known. However, sponges inhabiting freshwaters have been largely ignored despite having widespread distributions and often high local abundances. We used natural abundance stable isotope signatures of carbon and nitrogen (δ ¹³C and δ ¹⁵N) to infer the primary food source of the cosmopolitan freshwater sponge Spongilla lacustris. Our results suggest that S. lacustris feed largely on pelagic resources and may therefore link pelagic and benthic food webs. A facultative association between S. lacustris and endosymbiotic green algae caused S. lacustris to have significantly depleted carbon and nitrogen signatures that may reflect carbon and nitrogen exchange between sponges and their symbiotic algae. Isotopic data from specialist sponge consumers demonstrated that sponges hosting zoochlorellae were the major component of the diet of the spongillafly Climacia areolaris and the sponge-eating caddisfly Ceraclea resurgens suggesting that the symbiosis between freshwater sponges and algae is important to sponge predator trophic ecology. Our results help define the role of sponges in freshwater ecosystems and shed new light on the evolution and ecological consequences of a complex tri-trophic symbiosis involving freshwater sponges, zoochlorellae, and spongivorous insects.     

Upper Triassic (Carnian) reef biota from the Sambosan Accretionary Complex, Kyushu, Japan

Calcified sponges, algae, and reef problematica are abundant yet poorly known from the Triassic of Japan. They are abundant in shallow-water carbonate, redeposited blocks of the Sambosan Accretionary Complex, Konosé Group, and southern Kyushu. Based on study of thin-sections from reef limestone exposed along the Kuma River, some important organisms and reef microfacies are described, which seem typical of Upper Triassic reef complexes. The most abundant reef organisms are hypercalcified sponges, including sphinctozoans, inozoans and chaetetids, followed by cyanophycean algae (including “Tubiphytes”-like organisms), and solenoporacean red algae. Loose sponge spicules in one thin-section also indicate the occurrence of rare hexactinellid sponges. Chambered demosponges described from the Konosé carbonate rocks include Solenolmia manon manon (Münster), Colospongia sp., Jablonskyia andrusovi (Jablonsky), several unidentified chambered sponges as well as the inozoid Permocorynella sp. 1 and Permocorynella sp. 2. Also present are chaetetid sponges and solenoporacean red algae belonging to Parachaetetes cassianus (Flügel) and Parachaetetes? sp. or Solenopora? sp. Especially abundant in thin-sections are cyanophyceans and “Tubiphytes”-like organisms. Among the organisms is Cladogirvanella Ott and Hedstroemia sp. The composition of the biota and presence of typical problematic organisms increases our knowledge of shallow-water Upper Triassic carbonate rocks in a remote setting in western Panthalassa. The composition of the biota indicates a mostly Carnian age. Most comparable organisms are known from both the northeastern and southern Tethys.     

Microscopical techniques reveal the in situ microbial association inside Aplysina aerophoba, Nardo 1886 (Porifera, Demospongiae, Verongida) almost exclusively consists of cyanobacteria

Sponges (Porifera) are aquatic, sessile filter feeders. As such they are permanently exposed to bacteria in the seawater. Molecular data recovered from sponges by PCR shows a high diversity in bacterial DNA. Hence, sponges are considered to live in close association with a diverse and abundant bacterial community. To recover the spatial distribution of bacteria in sponges we retrieved histological sections of Aplysina aerophoba fixed in situ. By combining signals from fluorescence in situ hybridization (FISH), light microscopy and scanning electron microscopy we revealed a detailed histological picture of the spatial organization of the sponge microbial association within the sponges. Our histological results confirm a high abundance of cyanobacteria inside A. aerophoba while other living bacteria are almost absent. This detailed insight into sponge microbiology could only be achieved by the combination of careful sample preparation and different microscopical and histological methods. It also shows the need to confirm molecular datasets in situ and with a high spatial resolution.     

Bacterial Diversity Associated with Cinachyra cavernosa and Haliclona pigmentifera,Cohabiting Sponges in the Coral Reef Ecosystem of Gulf of Mannar,Southeast Coast of India

Sponges are abundant, diverse and functionally important organisms of coral reef ecosystems. Sponge-associated microorganisms have been receiving greater attention because of their significant contribution to sponge biomass, biogeochemical cycles and biotechnological potentials. However, our understanding of the sponge microbiome is limited to a few species of sponges from restricted geographical locations. Here, we report for the first time the bacterial diversity of two cohabiting sponges, viz. Cinachyra cavernosa and Haliclona pigmentifera, as well as that in the ambient water from the coral reef ecosystems of the Gulf of Mannar, located along the southeast coast of India. Two hundred and fifty two clones in the 16S rRNA gene library of these sponges were grouped into eight distinct phyla, of which four belonged to the core group that are associated only with sponges. Phylogenetic analysis of the core bacteria showed close affinity to other sponge-associated bacteria from different geographical locations. γ-Proteobacteria, Chloroflexi, Planctomycetes and Deferribacter were the core groups in C. cavernosa while β and δ-Proteobacteria performed this role in H. pigmentifera. We observed greater OTU diversity for C. cavernosa (H^ǀ 2.07) compared to H. pigmentifera (H^ǀ 1.97). UniFrac analysis confirmed the difference in bacterial diversity of the two sponge species and also between the sponges and the reef water (p<0.001). The results of our study restate the existence of a host driven force in shaping the sponge microbiome.     

Free amino acids in some sponges

Most invertebrates, particularly those of marine origin, have relatively high concentrations of free amino acids which are considered an important constituent of their osmoregulatory mechanisms [1]. Very little information is available on the free amino acid distribution in Porifera [2,3]. Common amino acids in some sponges were recognised by paper chromatography by Inskip and Cassidy [4] and Ackermann et al. [5,6] included a few sponges in their survey of the occurence of nitrogen compounds in marine invertebrates. More recently Bergquist and Hartman [7] surveyed semiquantitatively the distribution of free amino acids in several sponges. In the present paper we report on the amino acid composition of 12 species of sponges belonging to the class Demospongiae as a part of a study on the metabolites of Porifera [8]. Fresh sponges were extracted with aqueous ethanol. The organic solvent was removed and the aqueous solution, after removal of the ether soluble compounds, was separated into cationic, anionic and neutral fractions by ion-exchange chromatography. The cation fraction was analysed for amino acids using an automatic amino acid analyser. The results, which are presented in Table 1, show that all species of sponges examined have a similar composition in common amino acids. Glycine almost always appears as the dominant protein amino acid, followed by high concentrations of alanine and glutamic acid, whereas relatively lower concentrations of basic amino acids are present. In Axinella cannabina, Chondrosia reniformis, Chondrilla nucula, Cliona viridis and Hymeniacidon sanguinea, glycine represents more than 77% of the total amino acids. The high percentage of free glycine (90.4%) in Chondrosia reniformis is noteworthy. The anionic and the neutral fractions were examined for sulfur-containing amino acids using PC. Taurine (Table 2) was detected in all the Porifera examined; this is in agreement with previous observations [5–7]. N-Methyltaurine was identified in some of the species examined, whereas neither N,N-dimethyltaurine nor N,N,N-trimethyltaurine were found.     

Transplantation of marine sponges to different conditions of light and current

Transplantation was employed to determine how marine sponges grow in different in situ conditions of light and current. The growth of Verongia aerophoba (Schmidt), which contained symbiotic cyanobacteria. was enhanced in light, particularly when sediment was excluded by a clear shield. V. cavernicola Vacelet and Chondrosia reniformis Nardo. which did not contain cyanobacteria, grew preferentially in the shade and were inhibited by light. The growth of Petrosia ficiformis (Poirct) and Chondrilla nucula Schmidt, which may or may not contain cyanobacteria. did not appear to be favoured by either light or shade. The growth of sponges in lower current speeds was considerably reduced ; this reduction was. however, partially reversed in those sponges with cyanobacteria when grown in the light. Presumably symbiotic cyanobacteria are beneficial to sponges growing in the light because they transfer photosynthetically fixed nutrient and shield the underlying tissue. Significant morphological differences were observed in sponges grown under different environmental conditions.     

Promising antiparasitic agents from marine sponges

Parasitic diseases especially those prevail in tropical and subtropical regions severely threaten the lives of people due to available drugs found to be ineffective as several resistant strains have been emerged. Due to the complexity of the marine environment, researchers considered it as a new field to search for compounds with therapeutic efficacy, marine sponges represents the milestone in the discovery of unique compounds of potent activities against parasitic infections. In the present article, literatures published from 2010 until March 2021 were screened to review antiparasitic potency of bioactive compounds extracted from marine sponges. 45 different genera of sponges have been studied for their antiparasitic activities. The antiparasitic activity of the crude extract or the compounds that have been isolated from marine sponges were assayed in vitro against Plasmodium falciparum, P. berghei, Trypanosoma brucei rhodesiense, T. b. brucei, T. cruzi, Leishmania donovani, L. tropica, L. infantum, L. amazonesis, L. major, L. panamesis, Haemonchus contortus and Schistosoma mansoni. The majority of antiparastic compounds extracted from marine sponges were related to alkaloids and peroxides represent the second important group of antiparasitic compounds extracted from sponges followed by terpenoids. Some substances have been extracted and used as antiparasitic agents to a lesser extent like steroids, amino acids, lipids, polysaccharides and isonitriles. The activities of these isolated compounds against parasites were screened using in vitro techniques. Compounds' potent activity in screened papers was classified in three categories according to IC₅₀: low active or inactive, moderately active and good potent active.     

Bacterial community diversity associated with four marine sponges from the South China Sea based on 16S rDNA-DGGE fingerprinting

Culture-independent 16S rDNA-DGGE fingerprinting and phylogenetic analysis were used to reveal the community structure and diversity of the predominant bacteria associated with the four sponges Stelletta tenui, Halichrondria, Dysidea avara, and Craniella australiensis from the South China Sea for the first time. Sponge total community DNA extracted with a direct grinding disruption based method was used successfully after series dilution for 16S rDNA PCR amplification, which simplifies the current procedure and results in good DGGE banding profiles. 16S rDNA-V3 fragments from 42 individual DGGE bands were sequenced and the detailed corresponding bacteria were found in sponges for the fist time based on BLAST results. The sponge-associated bacteria are sponge host-specific because each of the tested four sponges from the same geographical location has different predominant bacterial diversity. Proteobacteria, e.g. α, β and γ subdivisions, make up the majority of the predominant bacteria in sponges and are perhaps in close symbiotic relationship with sponges. Though similar bacteria with close phylogenetic relationships were found among different sponges, the sponge-associated predominant bacterial community structures differ. Sponge C. australiensis has the greatest bacterial diversity, with the four bacteria phyla Proteobacteria, Bacteroidetes, Firmicutes, and Actinobacteria, followed by the sponge D. avara with the two phyla Proteobacteria and Bacteroidetes, and the sponges S. tenui and Halichrondria with the phylum Proteobacteria. DGGE fingerprint-based analysis should ideally be integrated with band cloning and sequencing, phylogenetic analysis and molecular techniques to obtain precise results in terms of the microbial community and diversity.