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Structure of Hierridin C, Synthesis of Hierridins B and C, and Evidence for Prevalent Alkylresorcinol Biosynthesis in Picocyanobacteria

Publication . Costa, Margarida; Sampaio-Dias, Ivo E.; Castelo-Branco, Raquel; Scharfenstein, Hugo; Rezende de Castro, Roberta; Silva, Artur; Schneider, Maria Paula C.; Araújo, Maria João; Martins, Rosário; Domingues, Valentina F.; Nogueira, Fátima; Camões, Vera; Vasconcelos, Vitor M.; Leão, Pedro N.

Small, single-celled planktonic cyanobacteria are ubiquitous in the world's oceans yet tend not to be perceived as secondary metabolite-rich organisms. Here we report the isolation and structure elucidation of hierridin C, a minor metabolite obtained from the cultured picocyanobacterium Cyanobium sp. LEGE 06113. We describe a simple, straightforward synthetic route to the scarcely produced hierridins that relies on a key regioselective halogenation step. In addition, we show that these compounds originate from a type III PKS pathway and that similar biosynthetic gene clusters are found in a variety of bacterial genomes, most notably those of the globally distributed picocyanobacteria genera Prochlorococcus, Cyanobium and Synechococcus.

2019-02Journal article

Open access

Using early life stages of marine animals to screen the toxicity of priority hazardous and noxious substances

Publication . Cunha, Isabel; Torres, Tiago; Oliveira, Helena; Martins, Rosário; McGowan, Thomas; Sheahan, David; Santos, Miguel Machado

This study provides toxicity values for early life stages (ELS) of two phylogenetically distinct marine animal taxa, the sea urchin (Paracentrotus lividus), a deuterostome invertebrate, and the turbot (Scophthalmus maximus), a vertebrate (teleost), when challenged by six hazardous and noxious substances (HNS): aniline, butyl acrylate, m-cresol, cyclohexylbenzene, hexane and trichloroethylene. The aim of the study was to provide preliminary information on toxic effects of representative and relevant priority HNS to assess the risk posed by spills to marine habitats and therefore improve preparedness and the response at the operational level. Selection criteria to include each compound in the study were (1) inclusion in the HASREP (2005) list; (2) presence on the priority list established by Neuparth et al. (2011); (3) paucity of toxicological data (TOXnet and ECOTOX) for marine organisms; (4) behaviour in the water according to the categories defined by the European Behaviour classification system (GESAMP 2002), by selecting compounds with different behaviours in water; and (5) physicochemical and toxicological properties, where available, in order to anticipate the most toxic compounds. Aniline and m-cresol were the most toxic compounds with no observed apical effect concentration (NOAEC) values for sea urchin ranging between 0.01 and 0.1 mg/L, followed by butyl acrylate and cyclohexylbenzene with NOAECs ranging between 0.1 and 1.0 mg/L and trichloroethylene with NOAEC values that were in the range between 1 and 10 mg/L, reflecting their behaviour in water, mostly vapour pressure, but also solubility and log Kow. Hexane was toxic only for turbot embryos, due to its neurotoxic effects, and not for sea urchin larvae, at concentrations in the range between 1 and 10 mg/L. The concentrations tested were of the same order of magnitude for both species, and it was observed that sea urchin embryos (length of the longest arm) are more sensitive than turbot eggs larvae (hatching and cumulative mortality rates) to the HNS tested (except hexane). For this specific compound, concentrations up to 70 mg/L were tested in sea urchin larvae and no effects were observed on the length of the larvae. Both tests were found to be complementary depending on behaviour in water and toxicity target of the compounds analysed.

2017Journal article

Open access

Chlorella vulgaris (SAG 211-12) biofilm formation capacity and proposal of a rotating flat plate photobioreactor for more sustainable biomass production

Publication . Melo, Miguel; Fernandes, Sílvia; Caetano, Nídia; Borges, Maria Teresa

Difficulties and cost of suspended microalgal biomass harvest and processing can be overcome by cultivating microalgae as biofilms. In the present work, a new photoautotrophic biofilm photobioreactor, the rotating flat plate photobioreactor (RFPPB), was developed aiming at a cost-effective production of Chlorella vulgaris (SAG 211-12), a strain not frequently referred in the literature but promising for biofuel production. Protocols were developed for evaluating initial adhesion to different materials and testing the conditions for biofilm formation. Polyvinyl chloride substrate promoted higher adhesion and biofilm production, followed by polypropylene, polyethylene, and stainless steel. The new RFPPB was tested, aiming at optimizing incident light utilization, minimizing footprint area and simplifying biomass harvesting. Tests show that the photobioreactor is robust, promotes biofilm development, and has simple operation, small footprint, and easy biomass harvest. Biomass production (dry weight) under non-optimized conditions was 3.35 g m−2, and areal productivity was 2.99 g m−2 day−1. Lipid content was 10.3% (dw), with high PUFA content. These results are promising and can be improved by optimizing some operational parameters, together with evaluation of long-term photobioreactor maximum productivity.

2017Journal article

Open access

Revealing the potential of cyanobacteria in cosmetics and cosmeceuticals — A new bioactive approach

Publication . Morone, Janaína; Alfeus, Anna; Vasconcelos, Vitor; Martins, Rosário

The growing concern over appearance, health and aging has driven the exploration for cosmetics based on natural sources. Alongside with plants, algae and eukaryotic microalgae, cyanobacteria have been explored for the isolation of compounds with potential application in the cosmetic and cosmeceutical field. The long evolutionary history of cyanobacteria and exposure to environmental stress conditions seems to be the basis for the production of compounds with protective roles against external factors, such as desiccation, UV radiation and salinity. The production of exopolysaccharides, UV-protectors such as mycrosporine like amino acids and scytonemin, and antioxidant and anti-inflammatory compounds, by a wide range of cyanobacteria genera, coupled with a growing demand for natural origin products, places these organisms in the investigation line linked to cosmetics. The low nutritional requirements for large scale culture and the possibility to increase compounds production by manipulating culture conditions, also highlights the importance of these organisms as an alternative and a promising source for cosmetics based on nature. In this review, a general overview of the state of the art regarding the potential of cyanobacteria for the cosmetic and cosmeceutical industry is provided, emphasizing the main properties required in skin care formulations.

2019Journal article

Open access