Browsing by Author "Ramos, Vitor"
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- Antitumor activity of hierridin B, a cyanobacterial secondary metabolite found in both filamentous and unicellular marine strainsPublication . Leão, Pedro N.; Costa, Margarida; Ramos, Vitor; Pereira, Alban R.; Fernandes, Virgínia C.; Domingues, Valentina F.; Gerwick, William H.; Vasconcelos, Vítor; Martins, RosárioCyanobacteria are widely recognized as a valuable source of bioactive metabolites. The majority of such compounds have been isolated from so-called complex cyanobacteria, such as filamentous or colonial forms, which usually display a larger number of biosynthetic gene clusters in their genomes, when compared to free-living unicellular forms. Nevertheless, picocyanobacteria are also known to have potential to produce bioactive natural products. Here, we report the isolation of hierridin B from the marine picocyanobacterium Cyanobium sp. LEGE 06113. This compound had previously been isolated from the filamentous epiphytic cyanobacterium Phormidium ectocarpi SAG 60.90, and had been shown to possess antiplasmodial activity. A phylogenetic analysis of the 16S rRNA gene from both strains confirmed that these cyanobacteria derive from different evolutionary lineages. We further investigated the biological activity of hierridin B, and tested its cytotoxicity towards a panel of human cancer cell lines; it showed selective cytotoxicity towards HT-29 colon adenocarcinoma cells.
- Culture-dependent characterization of cyanobacterial diversity in the intertidal zones of the Portuguese coast: A polyphasic studyPublication . Brito, Ângela; Ramos, Vitor; Seabra, Rui; Santos, Arlete; Santos, Catarina; Lopo, Miguel; Ferreira, Sérgio; Martins, António; Mota, Rita; Frazão, Bárbara; Martins, Rosario; Vasconcelos, Vítor; Tamagnini, PaulaCyanobacteria are important primary producers, and many are able to fix atmospheric nitrogen playing a key role in the marine environment. However, not much is known about the diversity of cyanobacteria in Portuguese marine waters. This paper describes the diversity of 60 strains isolated from benthic habitats in 9 sites (intertidal zones) on the Portuguese South and West coasts. The strains were characterized by a morphological study (light and electron microscopy) and by a molecular characterization (partial 16S rRNA, nifH, nifK, mcyA, mcyE/ndaF, sxtI genes). The morphological analyses revealed 35 morphotypes (15 genera and 16 species) belonging to 4 cyanobacterial Orders/Subsections. The dominant groups among the isolates were the Oscillatoriales. There is a broad congruence between morphological and molecular assignments. The 16S rRNA gene sequences of 9 strains have less than 97% similarity compared to the sequences in the databases, revealing novel cyanobacterial diversity. Phylogenetic analysis, based on partial 16S rRNA gene sequences showed at least 12 clusters. One-third of the isolates are potential N2-fixers, as they exhibit heterocysts or the presence of nif genes was demonstrated by PCR. Additionally, no conventional freshwater toxins genes were detected by PCR screening.
- Cyanobacterial diversity held in microbial biological resource centers as a biotechnological asset: the case study of the newly established LEGE culture collectionPublication . Ramos, Vitor; Morais, João; Castelo-Branco, Raquel; Pinheiro, Ângela; Martins, Joana; Regueiras, Ana; Pereira, Ana L.; Lopes, Viviana R.; Frazão, Bárbara; Gomes, Dina; Moreira, Cristiana; Costa, Maria Sofia; Brûle, Sébastien; Faustino, Silvia; Martins, Rosario; Saker, Martin; Osswald, Joana; Leão, Pedro N.; Vasconcelos, Vitor M.Cyanobacteria are a well-known source of bioproducts which renders culturable strains a valuable resource for biotechnology purposes. We describe here the establishment of a cyanobacterial culture collection (CC) and present the first version of the strain catalog and its online database (http://lege.ciimar.up.pt/). The LEGE CC holds 386 strains, mainly collected in coastal (48%), estuarine (11%), and fresh (34%) water bodies, for the most part from Portugal (84%). By following the most recent taxonomic classification, LEGE CC strains were classified into at least 46 genera from six orders (41% belong to the Synechococcales), several of them are unique among the phylogenetic diversity of the cyanobacteria. For all strains, primary data were obtained and secondary data were surveyed and reviewed, which can be reached through the strain sheets either in the catalog or in the online database. An overview on the notable biodiversity of LEGE CC strains is showcased, including a searchable phylogenetic tree and images for all strains. With this work, 80% of the LEGE CC strains have now their 16S rRNA gene sequences deposited in GenBank. Also, based in primary data, it is demonstrated that several LEGE CC strains are a promising source of extracellular polymeric substances (EPS). Through a review of previously published data, it is exposed that LEGE CC strains have the potential or actual capacity to produce a variety of biotechnologically interesting compounds, including common cyanotoxins or unprecedented bioactive molecules. Phylogenetic diversity of LEGE CC strains does not entirely reflect chemodiversity. Further bioprospecting should, therefore, account for strain specificity of the valuable cyanobacterial holdings of LEGE CC.
- Picocyanobacteria from a clade of marine cyanobium revealed bioactive potential against microalgae, bacteria, and marinePublication . Costa, Maria Sofia; Costa, Margarida; Ramos, Vitor; Leão, Pedro N.; Barreiro, Aldo; Vasconcelos, Vítor; Martins, RosarioThe production of bioactive compounds either toxic or with pharmacological applications by cyanobacteria is well established. However, picoplanktonic forms within this group of organisms have rarely been studied in this context. In this study, the toxicological potential of picocyanobacteria from a clade of marine Cyanobium strains isolated from the Portuguese coast was examined using different biological models. First, strains were identified by applying morphological and molecular approaches and cultured under lab conditions. A crude extract and three fractions reflecting a preliminary segregation of lipophilic metabolites were tested for toxicity with the marine microalga Nannochloropsis sp., the bacteria Pseudomonas sp., the brine shrimp Artemia salina, and fertilized eggs of the sea urchin Paracentrotus lividus. No significant apparent adverse effects were noted against Artemia salina. However, significant adverse effects were found in all other assays, with an inhibition of Nannochloropsis sp. and Pseudomonas sp. growth and marked reduction in Paracentrotus lividus larvae length. The results obtained indicated that Cyanobium genus may serve as a potential source of interesting bioactive compounds and emphasize the importance of also studying smaller picoplanktonic fractions of marine cyanobacteria.
- State of the Art of Palytoxin and Analogs Analytical Methods for Seafood MonitoringPublication . Vasconcelos, Vitor; Azevedo, Joana; Silva, Marisa; Ramos, VitorPalytoxin group (PLTXs) are produced by marine organisms, like zoanthids (Palythoa) and benthic dinoflagellates (Ostreopsis). Besides originally found in tropical regions, reports on the presence of PLTXs in subtropical and temperate marine waters have grown considerably in the past decade.