Microbial diversity in the marine sponge Aplysina cavernicola (formerly Verongia cavernicola) analyzed by fluorescence in situ hybridization (FISH)

We have employed electronmicroscopical methods (SEM, TEM) to document the microbial community associated with the marine sponge Aplysina cavernicola (formerly Verongia cavernicola, class Demospongiae). Five dominant bacterial types were identified, three of which resemble the morphotypes originally described by Vacelet (1975). One bacterial type possesses morphological properties that are characteristic of the genus Planctomyces. In addition, morphologically uniform bacteria which reside inside the nuclei of host cells were observed. Using in situ hybridization with fluorescently labelled rRNA probes directed against known bacterial groups, the phylogenetic affiliation of the mesohyl bacteria was assessed. It could be shown that the vast majority of mesohyl bacteria belongs to the domain Bacteria with a low GC content. Among the Bacteria, the delta-Proteobacteria were most abundant, followed by the gamma-Proteobacteria and representatives of the Bacteroides cluster. Clusters of Gram-positive bacteria with a high GC content were also found consistently in low amounts. No hybridization signal was obtained with probes specific to the domain Archaea, to the alpha- and beta-Proteobacteria and to the Cytophaga/Flavobacterium cluster. This study describes for the first time the application of the “top-to-bottom approach” using 16S rRNA probes and in situ hybridization to assess the microbial diversity in Aplysina sponge

Field experimental evaluation of secondary metabolites from marine invertebrates as antifoulants Avaliação experimental de metabólitos secundários de invertebrados marinhos como antiincrustantes em campo

The crude organic extracts of the endemic gorgonian Phyllogorgia dilatata and two sponge species Aplysina fulva and Mycale microsigmatosa were evaluated for anti-fouling properties through field experiments. To investigate this property in ecologically meaningful conditions, crude extracts from these invertebrates were incorporated at concentrations naturally found in these marine organisms into a stable gel used as a substratum for fouling settlement. Crude extract from A. fulva showed no significant anti-fouling property at the natural concentrations used in the field experiments. In fact, fouling organisms settled significantly more on gels treated with A. fulva extract than on the control gel. On the other hand, both M. microsigmatosa and P. dilatata yielded crude extracts that exhibited a selective action inhibiting only the settlement of barnacles. The evidences obtained here by means of field experiments can provide a basis for future development of one kind of natural antifoulant technology to prevent marine biofouling.<br>As propriedades antiincrustantes dos extratos brutos da gorgônia endêmica Phyllogorgia dilatata e de duas espécies de esponja, Aplysina fulva e Mycale microsigmatosa, foram avaliadas por intermédio de ensaios de campo. Para investigar essas propriedades sob condições ecologicamente relevantes, as concentrações naturais dos extratos brutos encontrados nesses invertebrados foram incorporadas a um gel estável que serviu de substrato para o assentamento de organismos incrustantes. O extrato bruto de A. fulva não mostrou efeito antiincrustante na concentração natural usada nos experimentos. De fato, os organismos incrustantes colonizaram significativamente mais o gel contendo extrato de A. fulva do que o gel-controle. Por outro lado, ambos os invertebrados, M. microsigmatosa e P. dilatata, produzem extratos brutos que foram seletivamente ativos contra o estabelecimento de balanídeos. As evidências obtidas aqui, por meio de experimentos em campo, podem ser importantes subsídios para futuras investigações visando à aplicação industrial de produtos naturais antiincrustantes em tecnologias de prevenção da bioincrustação marinha