Search Results (28)

Cytostatics are contaminants of emerging concern. Their increasing presence in waste- and surface water is becoming a risk to aquatic life. Among them, 5-fluorouracil (5-FU) is one of the most frequently prescribed cytostatic drugs. 5-FU inhibits the thymidylate synthase activity, causing the depletion of thymidine nucleotides and misincorporation of uracil, and thus blocks DNA synthesis and replication. This study focuses on the influence of 5-FU on brackish and marine diatoms from the Baltic Sea, including Bacillaria cf. paxillifera, Gedaniella sp., Navicula perminuta, Nitzschia cf. aurariae, Skeletonema marinoi and Stephanocyclus meneghinianus, as well as natural microphytobenthos assemblages. The toxic effects of 5-FU were investigated in acute growth inhibition tests, which were performed using four types of media, i.e., artificial seawater with a salinity of 6.7, natural Baltic water, artificial seawater with a salinity of 22, and artificial seawater with the addition of cyclophosphamide and ifosfamide. The toxicity of 5-FU was checked for (1) each strain grown individually in all media, (2) six-strain mixed cultures grown in artificial seawater, and (3) natural microphytobenthic communities maintained in natural Baltic water. The diatom responses to 5-FU were species-specific. Growth conditions significantly modified the toxicity of 5-FU; tested strains were the most resistant to 5-FU when grown under optimal conditions, i.e., in natural Baltic water and/or at the optimal salinity. In the six-strain mixed cultures, higher 5-FU concentrations (>0.1 mg L⁻¹) shifted the dominance of diatom strains; the most resilient diatom S. meneghinianus replaced two other fast-growing strains, i.e., B. cf. paxillifera and Gedaniella sp. In the tested microphytobenthos assemblages, the highest biomass and species diversity were observed under the highest 5-FU concentrations (>5 mg L⁻¹). This indicated that the responses of complex species mixtures were governed by the ecophysiological features of their members and interactions among them, shaping the adaptive capacity of the entire assemblage. The introduction of the ecophysiological approach to toxicity testing seems to be crucial, and it would enable more realistic environmental risk assessment. Full article

Acne is one of the most common dermatological conditions, peaking during adolescence and early adulthood, affecting about 85% of individuals aged 12–24. Although often associated with teenage years, acne can occur at any age, impacting over 25% of women and 12% of men in their forties. Treatment strategies vary depending on the severity, including the use of topical gels or creams containing benzoyl peroxide and retinoids, antibiotics, and systemic or topical isotretinoin. However, these treatments can cause irritation, allergies, and other toxic side effects. Currently, there is no natural-based alternative for antibacterial photodynamic therapy targeting acne using marine drugs or extracts. Through a bioguided screening approach, we identified the ethanol extract of Skeletonema marinoi as highly phototoxic against three bacterial species associated with acne—Cutibacterium acnes, Staphylococcus aureus, and Staphylococcus epidermidis. This extract exhibited phototoxicity in planktonic bacteria under white and red light, disrupted bacterial biofilms, reduced sebum production but also showed phototoxicity in keratinocytes, highlighting the importance of the specific targeting of treatment areas. Further investigations, including fractionation and high-resolution structural analysis, linked the observed phototoxicity to a high concentration of pheophorbide a in the extract. Given its notable in vitro efficacy, this extract holds promising potential for clinical evaluation to manage mild acne. This discovery paves the way for further exploration of Skeletonema pigment extracts, extending their potential applications beyond acne phototherapy to include dermocosmetics, veterinary medicine, and other phototherapy uses. Full article

Microalgae are currently considered an attractive source of highly valuable metabolites potentially exploitable as anticancer agents, nutraceuticals and cosmeceuticals and for bioenergy purposes. Their ease of culturing and their high growth rates further promote their use as raw material for the production of specialty products. In the present paper, we focused our attention on specific glycerol-based lipid compounds, monoacylglycerols (MAGs), which displayed in our previous studies a selective cytotoxic activity against the haematological U-937 and the colon HCT-116 cancer cell lines. Here, we performed a quali/quantitative analysis of MAGs and total fatty acids (FAs) along with a profiling of the main lipid classes in a panel of 12 microalgal species, including diatoms and dinoflagellates. Our results highlight an inter- and intraspecific variability of MAG profile in the selected strains. Among them, Skeletonema marinoi (strain FE7) has emerged as the most promising source for possible biotechnological production of MAGs. Full article

Bivalves accumulate toxins produced by microalgae, thus becoming harmful for humans. However, little information is available about their toxicity to the bivalve itself. In the present work, the physiological stress and damage after the ingestion of toxic dinoflagellate species (Gymnodinium catenatum) and a diatom species (Skeletonema marinoi, which is non-toxic to humans but may be to grazers) in the oyster Magallana angulata are evaluated against a control treatment fed with the chlorophyte Tetraselmis sp. Oysters were exposed for two hours to a concentration of 4 × 10⁴ cells/L of G. catenatum and 2 × 10⁷ cells/L of S. marinoi. The biomarkers superoxide dismutase (SOD), catalase (CAT), glutathione S-Transferase, total Ubiquitin (Ubi) and Acetylcholinesterase (AchE) were assessed. The exposure of M. angulata to G. catenatum lead to a reduction in SOD and AchE activity and ubiquitin concentrations when compared to the control treatment. Moreover, it increased CAT activity in the adductor muscle, and maintained its activity in the other tissues tested. This may be related to the combination of reduced metabolism with the deployment of detoxification processes. S. marinoi also lead to a decrease in all biomarkers tested in the gills and digestive glands. Therefore, both species tested caused physiological alterations in M. angulata after two hours of exposure. Full article

The ever-growing demand for sea cucumbers is a threat to these echinoderms and their habitats; however, a way to relieve stock pressure lies in meeting demand through aquaculture. As such, this study aimed to improve the growth and survival percentage of Holothuria arguinensis during larval development, settlement and juvenile growth. Three diets of microalgae (Diet RbPt = Rhodomonas baltica + Phaeodactylum tricornutum; Diet RbSm = Rhodomonas baltica + Skeletonema marinoi; Diet RbCc = Rhodomonas baltica + Chaetoceros calcitrans) were administered daily to the larval phase. Additionally, three substrates were supplied (pvc rolls, wavy pvc plaques and tile) at three different depths in order to determine the most favourable for settlement. Lastly, the potential benefits on growth and survival from introducing macroalgae (Sacchoriza polyschides) in the juvenile diet were assessed over a period of 6 months. Despite larvae under diet RbPt having presented a larger mean width, H. arguinensis fed with Diet RbCc presented a higher settlement survival at the end of the trial. No preferences were noted among the tested substrates, regardless of diet. Lastly, juveniles with added S. polyschides in their diet showed increased growth in mean weight and length when compared to individuals that were not fed with this seaweed. Full article

In the last two decades, the phenomenon of macroaggregation has become more frequent in the Mediterranean Sea and beyond, but it has disappeared in the northern Adriatic. The aim of this study was to present, for the first time, the concentration of surface-active particles (SAP) at selected sampling stations in the northern Adriatic Sea, as well as phytoplankton and chlorophyll data and physical properties of seawater, in order to investigate the role of SAP in macroaggregation. We used an electrochemical method (polarography and amperometry) to directly and throughput characterize fragile organic material in terms of its dissolved and particulate state in seawater samples. The results show that the concentration of SAP is subject to seasonal variations and was generally higher in the western region. In addition, an increase in surfactant activity and concentration of SAP was detected in the subsurface layer and in the stratified column prior to the mucilage event, which may be related to the very high abundance of Skeletonema marinoi, a diatom characteristic of the winter bloom in the region. We noted an order of magnitude higher concentration of SAP than typically observed in late winter/early spring, which serves as a precursor to the macroaggregation that occurs under certain environmental and oceanographic conditions in marine systems. Full article

The exploration of natural preventive molecules for nutraceutical and pharmaceutical use has recently increased. In this scenario, marine microorganisms represent an underestimated source of bioactive products endowed with beneficial effects on health that include anti-oxidant, anti-inflammatory, differentiating, anti-tumor, and anti-angiogenic activities. Here, we tested the potential chemopreventive and anti-angiogenic activities of an extract from the marine coastal diatom Skeletonema marinoi Sarno and Zingone (Sm) on prostate cancer (PCa) and endothelial cells. We also tested one of the main carotenoids of the diatom, the xanthophyll pigment fucoxanthin (Fuco). Fuco from the literature is a potential candidate compound involved in chemopreventive activities. Sm extract and Fuco were able to inhibit PCa cell growth and hinder vascular network formation of endothelial cells. The reduced number of cells was partially due to growth inhibition and apoptosis. We studied the molecular targets by qPCR and membrane antibody arrays. Angiogenesis and inflammation molecules were modulated. In particular, Fuco downregulated the expression of Angiopoietin 2, CXCL5, TGFβ, IL6, STAT3, MMP1, TIMP1 and TIMP2 in both prostate and endothelial cells. Our study confirmed microalgae-derived drugs as potentially relevant sources of novel nutraceuticals, providing candidates for potential dietary or dietary supplement intervention in cancer prevention approaches. Full article

Polycarbamate is commonly used as an antifoulant coating on fishing nets in Japan. Although its toxicity to freshwater organisms has been reported, its toxicity to marine organisms is currently unknown. We conducted algal growth inhibition and crustacean immobilization tests to assess the effects of polycarbamate on marine organisms. We also evaluated the acute toxicity of the main components of polycarbamate, namely, dimethyldithiocarbamate and ethylenebisdithiocarbamate, to algae, which are the most sensitive tested organisms to polycarbamate. The toxicities of dimethyldithiocarbamate and ethylenebisdithiocarbamate partially explain that of polycarbamate. To assess the primary risk, we derived the predicted no-effect concentration (PNEC) for polycarbamate in a probabilistic manner using species sensitivity distributions. The 72 h no observed effect concentration (NOEC) of polycarbamate to the alga Skeletonema marinoi–dohrnii complex was 0.45 μg/L. The toxicity of dimethyldithiocarbamate may have contributed up to 72% of the toxicity observed for polycarbamate. The fifth percentile of hazardous concentration (HC₅) derived from the acute toxicity values was 0.48 μg/L. Comparison of previously reported environmental polycarbamate concentrations in Hiroshima Bay, Japan, to the PNEC estimated using the minimum NOEC and HC₅ suggest that polycarbamate currently poses a high ecological risk. Therefore, reducing the risk by restricting polycarbamate use is necessary. Full article

Chronic myeloid leukemia (CML) is a myeloproliferative disease that activates multiple signaling pathways, causing cells to produce higher levels of reactive oxygen species (ROS). Nicotinamide adenine dinucleotide phosphate (NADPH) oxidases (NOXs) are a major generator of ROS in leukemia, and marine natural products have shown promising activities for the treatment of hematopoietic malignancies. In the present study, we investigated the effect of the marine microalga Skeletonema marinoi (S.M.), a ubiquitous diatom that forms massive blooms in the oceans, on the human leukemia cell line K562. The effects of S.M. extract on cell viability, production of ROS, nitric oxide (NO), and apoptosis were examined. In this preliminary work, S.M. was able to decrease cell viability (p < 0.05) and increase apoptosis levels (p < 0.05) in K562 cells after 48 h of treatment. In addition, the levels of NOX, NO, and malondialdehyde (MDA) were reduced in K562-treated cells (p < 0.05), whereas the levels of SOD, CAT, and GPx increased during treatment (p < 0.05). Finally, analyzing Bax and Bcl-2 expression, we found a significant increase in the proapoptotic protein Bax and a sustained decrease in the antiapoptotic protein Bcl-2 (p < 0.05) in the K562-treated cells. Full article

Diatoms are a successful group of microalgae at the base of the marine food web. For hundreds of millions of years, they have shared common habitats with bacteria, which favored the onset of interactions at different levels, potentially driving the synthesis of biologically active molecules. To unveil their presence, we sequenced the genomes of bacteria associated with the centric diatom Thalassiosira rotula from the Gulf of Naples. Annotation of the metagenome and its analysis allowed the reconstruction of three bacterial genomes that belong to currently undescribed species. Their investigation showed the existence of novel gene clusters coding for new polyketide molecules, antibiotics, antibiotic-resistance genes and an ectoine production pathway. Real-time PCR was used to investigate the association of these bacteria with three different diatom clones and revealed their preference for T. rotula FE80 and Skeletonema marinoi FE7, but not S. marinoi FE60 from the North Adriatic Sea. Additionally, we demonstrate that although all three bacteria could be detected in the culture supernatant (free-living), their number is up to 45 times higher in the cell associated fraction, suggesting a close association between these bacteria and their host. We demonstrate that axenic cultures of T. rotula are unable to grow in medium with low salinity (<28 ppt NaCl) whereas xenic cultures can tolerate up to 40 ppt NaCl with concomitant ectoine production, likely by the associated bacteria. Full article

Microalgal biotechnology is gaining importance. However, key issues in the pipeline from species selection towards large biomass production still require improvements to maximize the yield and lower the microalgal production costs. This study explores a co-cultivation strategy to improve the bioactive compounds richness of the harvested microalgal biomass. Based on their biotechnological potential, two diatoms (Skeletonema marinoi, Cyclotella cryptica) and one eustigmatophyte (Nannochloropsis oceanica) were grown alone or in combination. Concentrations of ten vitamins (A, B₁, B₂, B₆, B₁₂, C, D₂, D₃, E and H), carotenoids and polyphenols, together with total flavonoids, sterols, lipids, proteins and carbohydrates, were compared. Moreover, antioxidant capacity and chemopreventive potential in terms inhibiting four human tumor-derived and normal cell lines proliferation were evaluated. Co-cultivation can engender biomass with emergent properties regarding bioactivity or bioactive chemical profile, depending on the combined species. The high vitamin content of C. cryptica or N. oceanica further enhanced (until 10% more) when co-cultivated, explaining the two-fold increase of the antioxidant capacity of the combined C. cryptica and N. oceanica biomass. Differently, the chemopreventive activity was valuably enhanced when coupling the two diatoms C. cryptica and S. marinoi. The results obtained in this pilot study promote microalgal co-cultivation as a valuable strategy aiming to boost their application in eco-sustainable biotechnology. Full article

Diatoms are one of the most widespread groups of microalgae on Earth. They possess extraordinary metabolic capabilities, including a great ability to adapt to different light conditions. Recently, we have discovered that the diatom Skeletonema marinoi produces the natural antioxidant ovothiol B, until then identified only in clams. In this study, we investigated the light-dependent modulation of ovothiol biosynthesis in S. marinoi. Diatoms were exposed to different light conditions, ranging from prolonged darkness to low or high light, also differing in the velocity of intensity increase (sinusoidal versus square-wave distribution). The expression of the gene encoding the key ovothiol biosynthetic enzyme, ovoA, was upregulated by high sinusoidal light mimicking natural conditions. Under this situation higher levels of reactive oxygen species and nitric oxide as well as ovothiol and glutathione increase were detected. No ovoA modulation was observed under prolonged darkness nor low sinusoidal light. Unnatural conditions such as continuous square-wave light induced a very high oxidative stress leading to a drop in cell growth, without enhancing ovoA gene expression. Only one of the inducible forms of nitric oxide synthase, nos2, was upregulated by light with consequent production of NO under sinusoidal light and darkness conditions. Our data suggest that ovothiol biosynthesis is triggered by a combined light stress caused by natural distribution and increased photon flux density, with no influence from the daily light dose. These results open new perspectives for the biotechnological production of ovothiols, which are receiving a great interest for their biological activities in human model systems. Full article

Diatoms are the dominant component of the marine phytoplankton. Several diatoms produce secondary metabolites, namely oxylipins, with teratogenic effects on their main predators, crustacean copepods. Our study reports the de novo assembled transcriptome of the calanoid copepod Calanus helgolandicus feeding on the oxylipin-producing diatom Skeletonema marinoi. Differential expression analysis was also performed between copepod females exposed to the diatom and the control flagellate Prorocentrum minimum, which does not produce oxylipins. Our results showed that transcripts involved in carbohydrate, amino acid, folate and methionine metabolism, embryogenesis, and response to stimulus were differentially expressed in the two conditions. Expression of 27 selected genes belonging to these functional categories was also analyzed by RT-qPCR in C. helgolandicus females exposed to a mixed solution of the oxylipins heptadienal and octadienal at the concentration of 10 µM, 15 µM, and 20 µM. The results confirmed differential expression analysis, with up-regulation of genes involved in stress response and down-regulation of genes associated with folate and methionine metabolism, embryogenesis, and signaling. Overall, we offer new insights on the mechanism of action of oxylipins on maternally-induced embryo abnormality. Our results may also help identify biomarker genes associated with diatom-related reproductive failure in the natural copepod population at sea. Full article

Diatom-derived oxylipins, including polyunsaturated aldehydes (PUA), are considered to have infochemical, allelochemical and bacteriostatic properties, with plausible roles as grazing deterrents and regulators of inter- and intraspecific competition. However, the extent and mechanisms of how PUA influence diatom–bacteria interactions remain unresolved. In this study, impacts on the diversity of the associated bacterial communities (microbiota) of two contrasting Skeletonema marinoi strains (a PUA and a non-PUA producer) were investigated under three nitrate conditions in batch culture. Further, the response of the culture microbiota was studied when spiked with PUA at ecologically relevant concentrations (86nM octadienal and 290nM heptadienal). Of the 741 identified OTUs, Proteobacteria was the most abundant phylum (62.10%), followed by Bacteroidetes (12.33%) and Firmicutes (6.11%). Escherichia/Shigella were the most abundant genera for all treatments. Similar communities were present in both spiked and non-spiked cultures suggesting they can tolerate PUA exposure at realistic concentrations. This study suggests that PUA are not major drivers of diatom–bacteria interactions in laboratory cultures. Full article

Oxygenated derivatives of fatty acids, collectively called oxylipins, are a highly diverse family of lipoxygenase (LOX) products well described in planktonic diatoms. Here we report the first investigation of these molecules in four benthic diatoms, Cylindrotheca closterium, Nanofrustulum shiloi, Cocconeis scutellum, and Diploneis sp. isolated from the leaves of the seagrass Posidonia oceanica from the Gulf of Naples. Analysis by hyphenated MS techniques revealed that C. closterium, N. shiloi, and C. scutellum produce several polyunsaturated aldehydes (PUAs) and linear oxygenated fatty acids (LOFAs) related to the products of LOX pathways in planktonic species. Diploneis sp. also produced other unidentified fatty acid derivatives that are not related to LOX metabolism. The levels and composition of oxylipins in the benthic species match their negative effects on the reproductive success in the sea urchin Paracentrotus lividus. In agreement with this correlation, the most toxic species N. shiloi revealed the same LOX pathways of Skeletonema marinoi and Thalassiosira rotula, two bloom-forming planktonic diatoms that affect copepod reproduction. Overall, our data highlight for the first time a major role of oxylipins, namely LOFAs, as info-chemicals for benthic diatoms, and open new perspectives in the study of the structuring of benthic communities. Full article