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Topical Collection "Bioactive Compounds from Marine Plankton"

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A topical collection in Marine Drugs (ISSN 1660-3397).

Editor

Collection Editor
Prof. Dr. Georg Pohnert

Institute for Inorganic and Analytical Chemistry, Friedrich-Schiller-University Jena, Lessingstr. 8, D-07743 Jena, Germany
Website | E-Mail
Fax: +49 3641 948172
Interests: marine chemical ecology; analytical chemistry; biosynthesis; oxylipins; lipids; terpenoids; phytoplankton

Topical Collection Information

Dear Collegues,

The inhabitants of the open water are under the influence of gradual changes in nutrients, light, temperature, mechanical cues. But only chemical signals have the potential to provide important directional information about conspecific, predatory or competing species. Hence, a very interesting chemistry has developed that has the power to shape the ecosystem. But these interesting metabolic tasks also resulted in the evolution of metabolites with interesting pharmacological activity. Bioactive metabolites include for example dissolved gases, lipids, oxylipins, polyketides, peptides, and proteins that demonstrate a surprising structural and functional complexity. In this collection we want to explore all topics in natural product chemistry of marine plankton and to illustrate current methodological and conceptual challenges in plankton research. Especially the complex interplay of toxins, nutrients and infochemicals shaping the marine plankton is of interest, but also the pharmacological activity, biosynthesis and genetics of the multitude of interesting metabolites will be covered in this collection.
Recent progress reveals an emerging field that calls for special attention and I therefore invite you to contribute your exciting work to the collection on “Marine Plankton” of Marine Drugs.

Prof. Dr. Georg Pohnert
Collection Editor

Submission

Manuscripts should be submitted online at www.mdpi.com by registering and logging in to this website. Once you are registered, click here to go to the submission form. Papers will be published continuously (as soon as accepted) and will be listed together on the collection website. Research articles, review articles as well as communications are invited. For planned papers, a title and short abstract (about 100 words) can be sent to the Editorial Office for announcement on this website.

Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are refereed through a peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Marine Drugs is an international peer-reviewed Open Access monthly journal published by MDPI.

Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 1800 CHF (Swiss Francs).

Keywords

  • marine plankton
  • phytoplankton
  • zooplankton
  • microbial loop
  • bioactive natural products
  • chemical ecology
  • chemical interactions
  • metabolites
  • lipids
  • oxylipins
  • red tides
  • polyketides
  • toxins

Published Papers (15 papers)

2016

Jump to: 2013

Open AccessArticle Chemical and Genetic Diversity of Nodularia spumigena from the Baltic Sea
Mar. Drugs 2016, 14(11), 209; doi:10.3390/md14110209
Received: 29 September 2016 / Revised: 26 October 2016 / Accepted: 2 November 2016 / Published: 10 November 2016
Abstract
Nodularia spumigena is a toxic, filamentous cyanobacterium occurring in brackish waters worldwide, yet forms extensive recurrent blooms in the Baltic Sea. N. spumigena produces several classes of non-ribosomal peptides (NRPs) that are active against several key metabolic enzymes. Previously, strains from geographically distant
[...] Read more.
Nodularia spumigena is a toxic, filamentous cyanobacterium occurring in brackish waters worldwide, yet forms extensive recurrent blooms in the Baltic Sea. N. spumigena produces several classes of non-ribosomal peptides (NRPs) that are active against several key metabolic enzymes. Previously, strains from geographically distant regions showed distinct NRP metabolic profiles. In this work, conspecific diversity in N. spumigena was studied using chemical and genetic approaches. NRP profiles were determined in 25 N. spumigena strains isolated in different years and from different locations in the Baltic Sea using liquid chromatography-tandem mass spectrometry (LC-MS/MS). Genetic diversity was assessed by targeting the phycocyanin intergenic spacer and flanking regions (cpcBA-IGS). Overall, 14 spumigins, 5 aeruginosins, 2 pseudaeruginosins, 2 nodularins, 36 anabaenopeptins, and one new cyanopeptolin-like peptide were identified among the strains. Seven anabaenopeptins were new structures; one cyanopeptolin-like peptide was discovered in N. spumigena for the first time. Based on NRP profiles and cpcBA-IGS sequences, the strains were grouped into two main clusters without apparent influence of year and location, indicating persistent presence of these two subpopulations in the Baltic Sea. This study is a major step in using chemical profiling to explore conspecific diversity with a higher resolution than with a sole genetic approach. Full article
Open AccessArticle Structure–Activity Relationship Studies Using Natural and Synthetic Okadaic Acid/Dinophysistoxin Toxins
Mar. Drugs 2016, 14(11), 207; doi:10.3390/md14110207
Received: 9 July 2016 / Revised: 7 August 2016 / Accepted: 31 October 2016 / Published: 4 November 2016
Abstract
Okadaic acid (OA) and the closely related dinophysistoxins (DTXs) are algal toxins that accumulate in shellfish and are known serine/threonine protein phosphatase (ser/thr PP) inhibitors. Phosphatases are important modulators of enzyme activity and cell signaling pathways. However, the interactions between the OA/DTX toxins
[...] Read more.
Okadaic acid (OA) and the closely related dinophysistoxins (DTXs) are algal toxins that accumulate in shellfish and are known serine/threonine protein phosphatase (ser/thr PP) inhibitors. Phosphatases are important modulators of enzyme activity and cell signaling pathways. However, the interactions between the OA/DTX toxins and phosphatases are not fully understood. This study sought to identify phosphatase targets and characterize their structure–activity relationships (SAR) with these algal toxins using a combination of phosphatase activity and cytotoxicity assays. Preliminary screening of 21 human and yeast phosphatases indicated that only three ser/thr PPs (PP2a, PP1, PP5) were inhibited by physiologically saturating concentrations of DTX2 (200 nM). SAR studies employed naturally-isolated OA, DTX1, and DTX2, which vary in degree and/or position of methylation, in addition to synthetic 2-epi-DTX2. OA/DTX analogs induced cytotoxicity and inhibited PP activity with a relatively conserved order of potency: OA = DTX1 ≥ DTX2 >> 2-epi-DTX. The PPs were also differentially inhibited with sensitivities of PP2a > PP5 > PP1. These findings demonstrate that small variations in OA/DTX toxin structures, particularly at the head region (i.e., C1/C2), result in significant changes in toxicological potency, whereas changes in methylation at C31 and C35 (tail region) only mildly affect potency. In addition to this being the first study to extensively test OA/DTX analogs’ activities towards PP5, these data will be helpful for accurately determining toxic equivalence factors (TEFs), facilitating molecular modeling efforts, and developing highly selective phosphatase inhibitors. Full article
Open AccessReview Extracellular Metabolites from Industrial Microalgae and Their Biotechnological Potential
Mar. Drugs 2016, 14(10), 191; doi:10.3390/md14100191
Received: 16 August 2016 / Revised: 23 September 2016 / Accepted: 9 October 2016 / Published: 20 October 2016
Abstract
Industrial microalgae, as a big family of promising producers of renewable biomass feedstock, have been commercially exploited for functional food, living feed and feed additives, high-value chemicals in nutraceuticals, cosmeceuticals, and chemical reagents. Recently, microalgae have also been considered as a group that
[...] Read more.
Industrial microalgae, as a big family of promising producers of renewable biomass feedstock, have been commercially exploited for functional food, living feed and feed additives, high-value chemicals in nutraceuticals, cosmeceuticals, and chemical reagents. Recently, microalgae have also been considered as a group that might play an important role in biofuel development and environmental protection. Almost all current products of industrial microalgae are derived from their biomass; however, large amounts of spent cell-free media are available from mass cultivation that is mostly unexploited. In this contribution we discuss that these media, which may contain a remarkable diversity of bioactive substances are worthy to be recovered for further use. Obviously, the extracellular metabolites from industrial microalgae have long been neglected in the development of production methods for valuable metabolites. With the advances in the last ten years, more and more structures and properties from extracellular metabolites have been identified, and the potential utilization over wide fields is attracting attention. Some of these extracellular metabolites can be potentially used as drugs, antioxidants, growth regulators or metal chelators. The purpose of this review is to provide an overview of the known extracellular metabolites from industrial microalgae which might be of commercial interest. The attention mainly focuses on the reports of extracellular bioactive metabolites and their potential application in biotechnology. Full article
Open AccessReview Antimicrobial Compounds from Eukaryotic Microalgae against Human Pathogens and Diseases in Aquaculture
Mar. Drugs 2016, 14(9), 159; doi:10.3390/md14090159
Received: 12 July 2016 / Revised: 20 August 2016 / Accepted: 24 August 2016 / Published: 2 September 2016
Abstract
The search for novel compounds of marine origin has increased in the last decades for their application in various areas such as pharmaceutical, human or animal nutrition, cosmetics or bioenergy. In this context of blue technology development, microalgae are of particular interest due
[...] Read more.
The search for novel compounds of marine origin has increased in the last decades for their application in various areas such as pharmaceutical, human or animal nutrition, cosmetics or bioenergy. In this context of blue technology development, microalgae are of particular interest due to their immense biodiversity and their relatively simple growth needs. In this review, we discuss about the promising use of microalgae and microalgal compounds as sources of natural antibiotics against human pathogens but also about their potential to limit microbial infections in aquaculture. An alternative to conventional antibiotics is needed as the microbial resistance to these drugs is increasing in humans and animals. Furthermore, using natural antibiotics for livestock could meet the consumer demand to avoid chemicals in food, would support a sustainable aquaculture and present the advantage of being environmentally friendly. Using natural and renewable microalgal compounds is still in its early days, but considering the important research development and rapid improvement in culture, extraction and purification processes, the valorization of microalgae will surely extend in the future. Full article
Open AccessArticle Screening of Diatom Strains and Characterization of Cyclotella cryptica as A Potential Fucoxanthin Producer
Mar. Drugs 2016, 14(7), 125; doi:10.3390/md14070125
Received: 30 April 2016 / Revised: 18 June 2016 / Accepted: 29 June 2016 / Published: 8 July 2016
Cited by 1
Abstract
Fucoxanthin has been receiving ever-increasing interest due to its broad health beneficial effects. Currently, seaweeds are the predominant source of natural fucoxanthin. However, the disappointingly low fucoxanthin content has impeded their use, driving the exploration of alternative fucoxanthin producers. In the present study,
[...] Read more.
Fucoxanthin has been receiving ever-increasing interest due to its broad health beneficial effects. Currently, seaweeds are the predominant source of natural fucoxanthin. However, the disappointingly low fucoxanthin content has impeded their use, driving the exploration of alternative fucoxanthin producers. In the present study, thirteen diatom strains were evaluated with respect to growth and fucoxanthin production potential. Cyclotella cryptica (CCMP 333), which grew well for fucoxanthin production under both photoautotrophic and heterotrophic growth conditions, was selected for further investigation. The supply of nitrate and light individually or in combination were all found to promote growth and fucoxanthin accumulation. When transferring heterotrophic cultures to light, fucoxanthin responded differentially to light intensities and was impaired by higher light intensity with a concomitant increase in diadinoxanthin and diatoxanthin, indicative of the modulation of Diadinoxanthin Cycle to cope with the light stress. Taken together, we, for the first time, performed the screening of diatom strains for fucoxanthin production potential and investigated in detail the effect of nutritional and environmental factors on C. cryptica growth and fucoxanthin accumulation. These results provide valuable implications into future engineering of C. cryptica culture parameters for improved fucoxanthin production and C. cryptica may emerge as a promising microalgal source of fucoxanthin. Full article

2013

Jump to: 2016

Open AccessReview Bioprospecting Marine Plankton
Mar. Drugs 2013, 11(11), 4594-4611; doi:10.3390/md11114594
Received: 10 July 2013 / Revised: 6 September 2013 / Accepted: 9 October 2013 / Published: 14 November 2013
Cited by 9
Abstract
The ocean dominates the surface of our planet and plays a major role in regulating the biosphere. For example, the microscopic photosynthetic organisms living within provide 50% of the oxygen we breathe, and much of our food and mineral resources are extracted from
[...] Read more.
The ocean dominates the surface of our planet and plays a major role in regulating the biosphere. For example, the microscopic photosynthetic organisms living within provide 50% of the oxygen we breathe, and much of our food and mineral resources are extracted from the ocean. In a time of ecological crisis and major changes in our society, it is essential to turn our attention towards the sea to find additional solutions for a sustainable future. Remarkably, while we are overexploiting many marine resources, particularly the fisheries, the planktonic compartment composed of zooplankton, phytoplankton, bacteria and viruses, represents 95% of marine biomass and yet the extent of its diversity remains largely unknown and underexploited. Consequently, the potential of plankton as a bioresource for humanity is largely untapped. Due to their diverse evolutionary backgrounds, planktonic organisms offer immense opportunities: new resources for medicine, cosmetics and food, renewable energy, and long-term solutions to mitigate climate change. Research programs aiming to exploit culture collections of marine micro-organisms as well as to prospect the huge resources of marine planktonic biodiversity in the oceans are now underway, and several bioactive extracts and purified compounds have already been identified. This review will survey and assess the current state-of-the-art and will propose methodologies to better exploit the potential of marine plankton for drug discovery and for dermocosmetics. Full article
Open AccessArticle A Stable-Isotope Mass Spectrometry-Based Metabolic Footprinting Approach to Analyze Exudates from Phytoplankton
Mar. Drugs 2013, 11(11), 4158-4175; doi:10.3390/md11114158
Received: 12 August 2013 / Revised: 13 September 2013 / Accepted: 1 October 2013 / Published: 29 October 2013
Cited by 5
Abstract
Phytoplankton exudates play an important role in pelagic ecology and biogeochemical cycles of elements. Exuded compounds fuel the microbial food web and often encompass bioactive secondary metabolites like sex pheromones, allelochemicals, antibiotics, or feeding attractants that mediate biological interactions. Despite this importance, little
[...] Read more.
Phytoplankton exudates play an important role in pelagic ecology and biogeochemical cycles of elements. Exuded compounds fuel the microbial food web and often encompass bioactive secondary metabolites like sex pheromones, allelochemicals, antibiotics, or feeding attractants that mediate biological interactions. Despite this importance, little is known about the bioactive compounds present in phytoplankton exudates. We report a stable-isotope metabolic footprinting method to characterise exudates from aquatic autotrophs. Exudates from 13C-enriched alga were concentrated by solid phase extraction and analysed by high-resolution Fourier transform ion cyclotron resonance mass spectrometry. We used the harmful algal bloom forming dinoflagellate Alexandrium tamarense to prove the method. An algorithm was developed to automatically pinpoint just those metabolites with highly 13C-enriched isotope signatures, allowing us to discover algal exudates from the complex seawater background. The stable-isotope pattern (SIP) of the detected metabolites then allowed for more accurate assignment to an empirical formula, a critical first step in their identification. This automated workflow provides an effective way to explore the chemical nature of the solutes exuded from phytoplankton cells and will facilitate the discovery of novel dissolved bioactive compounds. Full article
Open AccessReview Plastids of Marine Phytoplankton Produce Bioactive Pigments and Lipids
Mar. Drugs 2013, 11(9), 3425-3471; doi:10.3390/md11093425
Received: 15 May 2013 / Revised: 2 July 2013 / Accepted: 24 July 2013 / Published: 9 September 2013
Cited by 17
Abstract
Phytoplankton is acknowledged to be a very diverse source of bioactive molecules. These compounds play physiological roles that allow cells to deal with changes of the environmental constrains. For example, the diversity of light harvesting pigments allows efficient photosynthesis at different depths in
[...] Read more.
Phytoplankton is acknowledged to be a very diverse source of bioactive molecules. These compounds play physiological roles that allow cells to deal with changes of the environmental constrains. For example, the diversity of light harvesting pigments allows efficient photosynthesis at different depths in the seawater column. Identically, lipid composition of cell membranes can vary according to environmental factors. This, together with the heterogenous evolutionary origin of taxa, makes the chemical diversity of phytoplankton compounds much larger than in terrestrial plants. This contribution is dedicated to pigments and lipids synthesized within or from plastids/photosynthetic membranes. It starts with a short review of cyanobacteria and microalgae phylogeny. Then the bioactivity of pigments and lipids (anti-oxidant, anti-inflammatory, anti-mutagenic, anti-cancer, anti-obesity, anti-allergic activities, and cardio- neuro-, hepato- and photoprotective effects), alone or in combination, is detailed. To increase the cellular production of bioactive compounds, specific culture conditions may be applied (e.g., high light intensity, nitrogen starvation). Regardless of the progress made in blue biotechnologies, the production of bioactive compounds is still limited. However, some examples of large scale production are given, and perspectives are suggested in the final section. Full article
Open AccessArticle Production, Characterization, and Antioxidant Activity of Fucoxanthin from the Marine Diatom Odontella aurita
Mar. Drugs 2013, 11(7), 2667-2681; doi:10.3390/md11072667
Received: 23 April 2013 / Revised: 7 June 2013 / Accepted: 8 July 2013 / Published: 23 July 2013
Cited by 27
Abstract
The production, characterization, and antioxidant capacity of the carotenoid fucoxanthin from the marine diatom Odontella aurita were investigated. The results showed that low light and nitrogen-replete culture medium enhanced the biosynthesis of fucoxanthin. The maximum biomass concentration of 6.36 g L−1 and
[...] Read more.
The production, characterization, and antioxidant capacity of the carotenoid fucoxanthin from the marine diatom Odontella aurita were investigated. The results showed that low light and nitrogen-replete culture medium enhanced the biosynthesis of fucoxanthin. The maximum biomass concentration of 6.36 g L−1 and maximum fucoxanthin concentration of 18.47 mg g−1 were obtained in cultures grown in a bubble column photobioreactor (Ø 3.0 cm inner diameter), resulting in a fucoxanthin volumetric productivity of 7.96 mg L−1 day−1. A slight reduction in biomass production was observed in the scaling up of O. aurita culture in a flat plate photobioreactor, yet yielded a comparable fucoxanthin volumetric productivity. A rapid method was developed for extraction and purification of fucoxanthin. The purified fucoxanthin was identified as all-trans-fucoxanthin, which exhibited strong antioxidant properties, with the effective concentration for 50% scavenging (EC50) of 1,1-dihpenyl-2-picrylhydrazyl (DPPH) radical and 2,2′-Azino-bis(3-ethylbenzthiazoline-6-sulfonic acid (ABTS) radical being 0.14 and 0.03 mg mL−1, respectively. Our results suggested that O. aurita can be a natural source of fucoxanthin for human health and nutrition. Full article
Open AccessArticle Effect of Grazing-Mediated Dimethyl Sulfide (DMS) Production on the Swimming Behavior of the Copepod Calanus helgolandicus
Mar. Drugs 2013, 11(7), 2486-2500; doi:10.3390/md11072486
Received: 11 April 2013 / Revised: 17 June 2013 / Accepted: 28 June 2013 / Published: 15 July 2013
Cited by 5
Abstract
Chemical interactions play a fundamental role in the ecology of marine foodwebs. Dimethyl sulfide (DMS) is a ubiquitous marine trace gas that acts as a bioactive compound by eliciting foraging behavior in a range of marine taxa including the copepod Temora longicornis.
[...] Read more.
Chemical interactions play a fundamental role in the ecology of marine foodwebs. Dimethyl sulfide (DMS) is a ubiquitous marine trace gas that acts as a bioactive compound by eliciting foraging behavior in a range of marine taxa including the copepod Temora longicornis. Production of DMS can rapidly increase following microzooplankton grazing on phytoplankton. Here, we investigated whether grazing-induced DMS elicits an increase in foraging behavior in the copepod Calanus helgolandicus. We developed a semi-automated method to quantify the effect of grazing-mediated DMS on the proportion of the time budget tethered females allocate towards slow swimming, typically associated with feeding. The pooled data showed no differences in the proportion of the 25 min time budget allocated towards slow swimming between high (23.6 ± 9.74%) and low (29.1 ± 18.33%) DMS treatments. However, there was a high degree of variability between behavioral responses of individual copepods. We discuss the need for more detailed species-specific studies of individual level responses of copepods to chemical signals at different spatial scales to improve our understanding of chemical interactions between copepods and their prey. Full article
Open AccessArticle Bioactive Compounds Offered in Microcapsules to Determine the Nutritional Value of Copepods’ Natural Diet
Mar. Drugs 2013, 11(7), 2459-2471; doi:10.3390/md11072459
Received: 9 April 2013 / Revised: 6 June 2013 / Accepted: 17 June 2013 / Published: 12 July 2013
Abstract
Experiments were performed, feeding Calanus pacificus seston and a food consisting of seston and microcapsules (μ-caps), i.e., protein and lipid μ-caps to test for potential biochemical limitation. Seston was collected off Scripps Pier (La Jolla, CA, USA). Whereas protein μ-caps were too
[...] Read more.
Experiments were performed, feeding Calanus pacificus seston and a food consisting of seston and microcapsules (μ-caps), i.e., protein and lipid μ-caps to test for potential biochemical limitation. Seston was collected off Scripps Pier (La Jolla, CA, USA). Whereas protein μ-caps were too small to be efficiently ingested, lipid μ-caps rich in ω3-highly-unsaturated fatty acids (ω3-HUFA) were ingested similarly to natural seston and lipids were assimilated. However, egg production experiments exhibited that animals fed with lipid μ-caps didn’t produce significantly more eggs than with seston of equal carbon concentration and egg production even declined when the diet consisted of 50% lipid μ-caps. Thus, the content of certain ω3-HUFA seemed to have been sufficiently high in seston to prevent limitation. Algal counts revealed that seston consisted mainly of plankton rich in those fatty acids, such as cryptophytes, dinoflagellates, diatoms, and ciliates in the edible size range. This might be characteristic for upwelling systems like the area off Southern California which are known for high trophic transfer efficiency. Full article
Open AccessArticle Domoic Acid Improves the Competitive Ability of Pseudo-nitzschia delicatissima against the Diatom Skeletonema marinoi
Mar. Drugs 2013, 11(7), 2398-2412; doi:10.3390/md11072398
Received: 17 May 2013 / Revised: 19 June 2013 / Accepted: 28 June 2013 / Published: 11 July 2013
Cited by 5
Abstract
Because domoic acid, a neurotoxic secondary metabolite produced by marine diatoms in the genus Pseudo-nitzschia, is hypothesized to be part of a high affinity iron uptake system, we investigated whether domoic acid could improve the competitive ability of Pseudo-nitzschia delicatissima, and
[...] Read more.
Because domoic acid, a neurotoxic secondary metabolite produced by marine diatoms in the genus Pseudo-nitzschia, is hypothesized to be part of a high affinity iron uptake system, we investigated whether domoic acid could improve the competitive ability of Pseudo-nitzschia delicatissima, and whether the availability of iron changed the outcome of competition experiments. We found that domoic acid had a slight negative effect on growth of the diatom Skeletonema marinoi when it was grown in monocultures. However, when S. marinoi was cultured with P. delicatissima the presence of domoic acid resulted in a reduction of S. marinoi cells by up to 38% and an increase in P. delicatissima cell numbers by up to 17% under iron replete conditions. Similar effects were not observed in low iron treatments. Domoic acid was not taken up by P. delicatissima cells. Overall, our results indicate that domoic acid can improve the competitive ability of Pseudo-nitzschia spp. and that iron is likely to be involved. This study provides an unusual example of indirect inhibition of competitor growth mediated by a secondary metabolite. Full article
Open AccessReview Alternative Sources of n-3 Long-Chain Polyunsaturated Fatty Acids in Marine Microalgae
Mar. Drugs 2013, 11(7), 2259-2281; doi:10.3390/md11072259
Received: 16 April 2013 / Revised: 16 May 2013 / Accepted: 21 May 2013 / Published: 27 June 2013
Cited by 40
Abstract
The main source of n-3 long-chain polyunsaturated fatty acids (LC-PUFA) in human nutrition is currently seafood, especially oily fish. Nonetheless, due to cultural or individual preferences, convenience, geographic location, or awareness of risks associated to fatty fish consumption, the intake of fatty
[...] Read more.
The main source of n-3 long-chain polyunsaturated fatty acids (LC-PUFA) in human nutrition is currently seafood, especially oily fish. Nonetheless, due to cultural or individual preferences, convenience, geographic location, or awareness of risks associated to fatty fish consumption, the intake of fatty fish is far from supplying the recommended dietary levels. The end result observed in most western countries is not only a low supply of n-3 LC-PUFA, but also an unbalance towards the intake of n-6 fatty acids, resulting mostly from the consumption of vegetable oils. Awareness of the benefits of LC-PUFA in human health has led to the use of fish oils as food supplements. However, there is a need to explore alternatives sources of LC-PUFA, especially those of microbial origin. Microalgae species with potential to accumulate lipids in high amounts and to present elevated levels of n-3 LC-PUFA are known in marine phytoplankton. This review focuses on sources of n-3 LC-PUFA, namely eicosapentaenoic and docosahexaenoic acids, in marine microalgae, as alternatives to fish oils. Based on current literature, examples of marketed products and potentially new species for commercial exploitation are presented. Full article
Open AccessArticle Extract from the Zooxanthellate Jellyfish Cotylorhiza tuberculata Modulates Gap Junction Intercellular Communication in Human Cell Cultures
Mar. Drugs 2013, 11(5), 1728-1762; doi:10.3390/md11051728
Received: 28 March 2013 / Revised: 24 April 2013 / Accepted: 25 April 2013 / Published: 22 May 2013
Cited by 9
Abstract
On a global scale, jellyfish populations in coastal marine ecosystems exhibit increasing trends of abundance. High-density outbreaks may directly or indirectly affect human economical and recreational activities, as well as public health. As the interest in biology of marine jellyfish grows, a number
[...] Read more.
On a global scale, jellyfish populations in coastal marine ecosystems exhibit increasing trends of abundance. High-density outbreaks may directly or indirectly affect human economical and recreational activities, as well as public health. As the interest in biology of marine jellyfish grows, a number of jellyfish metabolites with healthy potential, such as anticancer or antioxidant activities, is increasingly reported. In this study, the Mediterranean “fried egg jellyfish” Cotylorhiza tuberculata (Macri, 1778) has been targeted in the search forputative valuable bioactive compounds. A medusa extract was obtained, fractionated, characterized by HPLC, GC-MS and SDS-PAGE and assayed for its biological activity on breast cancer cells (MCF-7) and human epidermal keratinocytes (HEKa). The composition of the jellyfish extract included photosynthetic pigments, valuable ω-3 and ω-6 fatty acids, and polypeptides derived either from jellyfish tissues and their algal symbionts. Extract fractions showed antioxidant activity and the ability to affect cell viability and intercellular communication mediated by gap junctions (GJIC) differentially in MCF-7and HEKa cells. A significantly higher cytotoxicity and GJIC enhancement in MCF-7 compared to HEKa cells was recorded. A putative action mechanism for the anticancer bioactivity through the modulation of GJIC has been hypothesized and its nutraceutical and pharmaceutical potential was discussed. Full article
Open AccessArticle Lipid Peroxidation Is another Potential Mechanism besides Pore-Formation Underlying Hemolysis of Tentacle Extract from the Jellyfish Cyanea capillata
Mar. Drugs 2013, 11(1), 67-80; doi:10.3390/md11010067
Received: 22 September 2012 / Revised: 2 November 2012 / Accepted: 12 December 2012 / Published: 9 January 2013
Cited by 11
Abstract
This study was performed to explore other potential mechanisms underlying hemolysis in addition to pore-formation of tentacle extract (TE) from the jellyfish Cyanea capillata. A dose-dependent increase of hemolysis was observed in rat erythrocyte suspensions and the hemolytic activity of TE was
[...] Read more.
This study was performed to explore other potential mechanisms underlying hemolysis in addition to pore-formation of tentacle extract (TE) from the jellyfish Cyanea capillata. A dose-dependent increase of hemolysis was observed in rat erythrocyte suspensions and the hemolytic activity of TE was enhanced in the presence of Ca2+, which was attenuated by Ca2+ channel blockers (Diltiazem, Verapamil and Nifedipine). Direct intracellular Ca2+ increase was observed after TE treatment by confocal laser scanning microscopy, and the Ca2+ increase could be depressed by Diltiazem. The osmotic protectant polyethylenglycol (PEG) significantly blocked hemolysis with a molecular mass exceeding 4000 Da. These results support a pore-forming mechanism of TE in the erythrocyte membrane, which is consistent with previous studies by us and other groups. The concentration of malondialdehyde (MDA), an important marker of lipid peroxidation, increased dose-dependently in rat erythrocytes after TE treatment, while in vitro hemolysis of TE was inhibited by the antioxidants ascorbic acid—Vitamin C (Vc)—and reduced glutathione (GSH). Furthermore, in vivo hemolysis and electrolyte change after TE administration could be partly recovered by Vc. These results indicate that lipid peroxidation is another potential mechanism besides pore-formation underlying the hemolysis of TE, and both Ca2+ channel blockers and antioxidants could be useful candidates against the hemolytic activity of jellyfish venoms. Full article

Planned Papers

The below list represents only planned manuscripts. Some of these manuscripts have not been received by the Editorial Office yet. Papers submitted to MDPI journals are subject to peer-review.

Title: Chytrids infecting marine planktonic diatoms—Part 1: The role of chemotactic triggers in parasite-host recognition
Authors: Bettina Scholz 1,2, Frithjof Küpper 3, Wim Vyverman 4 and Ulf Karsten 5
Affiliations: 1 BioPol ehf., Einbúastig 2, 545 Skagaströnd, Iceland; 2 Faculty of Natural Resource Sciences, University of Akureyri, Borgir v. Nordurslod, IS 600 Akureyri, Iceland; 3 Oceanlab, University of Aberdeen, Main Street, Newburgh AB41 6AA, Scotland, United Kingdom; 4 Department of Biology, Section of Protistology and Aquatic Ecology, University of Ghent, Krijgslaan 281 S8, 9000 Ghent, Belgium; 5 Institute of Biological Sciences, Applied Ecology & Phycology, University of Rostock, Albert-Einstein-Strasse 3, 18059 Rostock, Germany
Abstract: All living organisms are subject to an almost permanent onslaught of parasitic organisms. Nevertheless, there is very little knowledge about such diseases in marine microalgae, and particularly about the presence and nature of chemical cues in parasite-host interactions. Thus, overall four host-parasite tandem cultures were used to test the chemotaxis of chytrid zoospores, utilizing Hellendahl staining jars divided in two compartments by nylon filters (Spectra/Mesh Nylon; mesh opening 5 µm). In the first compartment the four mixed diatom cultures infected by Chytridium spp, Rhizophydium type I, II and III were placed, whereas in the second one pre-soaked filters with trigger substances were adjusted on slides. As potential triggers, standards of eight carbohydrates, six amino acids and five fatty acids were used in individual and mixed solutions, respectively. In addition, cell extracts of the host diatoms Achnanthes, Pinnularia, Rhizosolenia and Chaetoceros, grown under a light: dark regime of 24:0 and 12:12, were also tested for their potential to trigger the chemotaxis of zoospores. After five days of incubation under standard culture conditions (f/2 with a salinity of 30, 10 °C, 40 µmol photons m‒2 s‒1, pH 8.5, 18:6 h light: dark regime) the filters were removed from the chambers, stained with Nile Red and DAPI and the number of zoospores were examined employing epifluorescence microscopy. In all tested cases, the filters pre-soaked with whole-cell extracts of the light-stressed hosts attracted the highest numbers of zoospores (86%), followed by the combined carbohydrate standard solution (76%). In contrast, almost all individual standards were found to be weak triggers for zoospore chemotaxis, varying only from 5.2–12.6% of the overall amount of zoospores in the chambers.
Keywords: cheamotaxis, chytrids, carbohydrates, amino acids, fatty acids, parasite-host interactions, zoospores

Title: Chytrids infecting marine diatoms—Part 2: First screening for host defence molecules and their biological activities
Authors: Bettina Scholz 1,2, Frithjof Küpper 3, Wim Vyverman 4 and Ulf Karsten 5
Affiliations: 1 BioPol ehf., Einbúastig 2, 545 Skagaströnd, Iceland; 2 Faculty of Natural Resource Sciences, University of Akureyri, Borgir v. Nordurslod, IS 600 Akureyri, Iceland; 3 Oceanlab, University of Aberdeen, Main Street, Newburgh AB41 6AA, Scotland, United Kingdom; 4 Department of Biology, Section of Protistology and Aquatic Ecology, University of Ghent, Krijgslaan 281 S8, 9000 Ghent, Belgium; 5 Institute of Biological Sciences, Applied Ecology & Phycology, University of Rostock, Albert-Einstein-Strasse 3, 18059 Rostock, Germany
Abstract: Overall 16 monoclonal cultures of four diatom hosts (Achnanthes, Pinnularia, Rhizosolenia and Chaetoceros) were found to be resistant against the onslaught of chytrid zoospores in a former study. Extracts and cell free filtrates of these cultures were used for phytochemical (e.g. phenols) and bioactivity screenings (algaecide, antimicrobial, and particularly zoospores of Chytridium spp, Rhizophydium type I, II and III in cross-experiments). The results of the phytochemical screening indicated in most of the tested extracts the presence of polyunsaturated fatty acids, phenols and aldehydes. Although in the bioactivity screening antimicrobial, particularly fungicide, effects were observed, zoospores of the chytrid parasites were only weakly affected. In additional experiments these zoospores were still not able to infect their hosts as it was found in the positive controls, suggesting that specific alterations or features of the diatom cell surfaces might have a key function in the resistance of the tested hosts.
Keywords: aldehydes, antimicrobials, chytrids, diatoms, host-parasite interactions, phytochemicals, polyunsaturated fatty acids

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