Secondary metabolites of seagrasses (Alismatales and Potamogetonales; Alismatidae): Chemical diversity, bioactivity, and ecological function

In vitro antibacterial, antibiofilm activities, and phytochemical properties of Posidonia oceanica (L.) Delile: An endemic Mediterranean seagrass

In the antibiotic resistance era, utilizing understudied sources for novel antimicrobials or antivirulence agents can provide new advances against antimicrobial resistant pathogens. In this study, we aimed to investigate antibacterial and antibiofilm activities of Posidonia oceanica (L.) Delile against Enterococcus faecalis ATCC 29212, Staphylococcus aureus ATCC 25923, Escherichia coli ATCC 25922 and Klebsiella pneumoniae ATCC 700603 and several S. aureus clinical isolates obtained from medical devices, including patient urinary catheters and breast implant infections, with varying antibiotic recalcitrance profiles. The ethanolic and methanolic extracts from P. oceanica rhizome exhibited significant antibacterial activity against E. faecalis and S. aureus, as well as drug resistant S. aureus clinical isolates. Furthermore, significant antibiofilm activity was observed against S. aureus and E. faecalis treated with ER, MR1, and MR2. P. oceanica extracts also exhibited synergistic antimicrobial activity with ciprofloxacin against E. faecalis, sensitizing E. faecalis to a lower ciprofloxacin concentration. Collectively, our data demonstrate the selective antibacterial and antibiofilm activity of the extracts of P. oceanica against Gram-positive bacteria and clinical isolates along with potentiation of current antibiotics, which suggests that P. oceanica can be further investigated as a potential source for novel therapeutic options in the treatment of drug resistant bacterial infections.

Zosterabisphenone B, a new diarylheptanoid heterodimer from the seagrass Zostera marina, induces apoptosis cell death in colon cancer cells and reduces tumour growth in mice

Colorectal cancer (CRC) is one of the most common malignant tumours worldwide. Diarylheptanoids, secondary metabolites isolated from Zostera marina, are of interest in natural products research due to their biological activities. Zosterabisphenone B (ZBP B) has recently been shown to inhibit the viability of CRC cells. The aim of this study was to investigate the therapeutic potential of ZBP B for targeting human CRC cells. Cell viability was determined using the MTT assay. Flow cytometry and Western blot analyses were used to assess apoptosis and autophagy. A CRC xenograft model was used to evaluate the in vivo effect of ZBP B. No cytotoxic effect on HCEC cells was observed in the in vitro experiments. ZBP B caused morphological changes in HCT116 colon cancer cells due to an increase in early and late apoptotic cell populations. Mechanistically, ZBP B led to an increase in cleaved caspase-3, caspase-8, caspase-9, PARP and BID proteins and a decrease in Bcl-2 and c-Myc proteins. In the xenograft model of CRC, ZBP B led to a reduction in tumour growth. These results indicate that ZBP B exerts a selective cytotoxic effect on CRC cells by affecting apoptotic signalling pathways and reducing tumour growth in mice. Taken together, our results suggest that ZBP B could be a lead compound for the synthesis and development of CRC drugs.

Small molecule in situ resin capture provides a compound first approach to natural product discovery

Culture-based microbial natural product discovery strategies fail to realize the extraordinary biosynthetic potential detected across earth's microbiomes. Here we introduce Small Molecule In situ Resin Capture (SMIRC), a culture-independent method to obtain natural products directly from the environments in which they are produced. We use SMIRC to capture numerous compounds including two new carbon skeletons that were characterized using NMR and contain structural features that are, to the best of our knowledge, unprecedented among natural products. Applications across diverse marine habitats reveal biome-specific metabolomic signatures and levels of chemical diversity in concordance with sequence-based predictions. Expanded deployments, in situ cultivation, and metagenomics facilitate compound discovery, enhance yields, and link compounds to candidate producing organisms, although microbial community complexity creates challenges for the later. This compound-first approach to natural product discovery provides access to poorly explored chemical space and has implications for drug discovery and the detection of chemically mediated biotic interactions.

The In Vitro Antioxidant and Anti-Inflammatory Activities of Selected Australian Seagrasses

Recent studies have shown that seagrasses could possess potential applications in the treatment of inflammatory disorders. Five seagrass species (Zostera muelleri, Halodule uninervis, Cymodocea rotundata, Syringodium isoetifolium, and Thalassia hemprichii) from the Great Barrier Reef (QLD, Australia) were thus collected, and their preliminary antioxidant and anti-inflammatory activities were evaluated. From the acetone extracts of five seagrass species subjected to 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical scavenging antioxidant assay, the extract of Z. muelleri had the highest activity (half minimal concentration of inhibition (IC50) = 138 µg/mL), with the aerial parts (IC50 = 119 µg/mL) possessing significantly higher antioxidant activity than the roots (IC50 ≥ 500 µg/mL). A human peripheral blood mononuclear cells (PBMCs) assay with bacterial lipopolysaccharide (LPS) activation and LEGENDplex cytokine analysis showed that the aerial extract of Z. muelleri significantly reduced the levels of inflammatory cytokines tumour necrosis factor alpha (TNF-α), interleukin (IL)-1β, and IL-6 by 29%, 74%, and 90%, respectively, relative to the LPS treatment group. The aerial extract was thus fractionated with methanol (MeOH) and hexane fraction, and purification of the MeOH fraction by HPLC led to the isolation of 4-hydroxybenzoic acid (1), luteolin (2), and apigenin (3) as its major constituents. These compounds have been previously shown to reduce levels of TNF-α, IL-1β, and IL-6 and represent some of the major bioactive components of Z. muelleri aerial parts. This investigation represents the first study of the antioxidant and anti-inflammatory properties of Z. muelleri and the first isolation of small molecules from this species. These results highlight the potential for using seagrasses in treating inflammation and the need for further investigation.

Synthesis and characterization of marine seagrass (Cymodocea serrulata) mediated titanium dioxide nanoparticles for antibacterial, antibiofilm and antioxidant properties

Cymodocea serrulata mediated titanium dioxide nanoparticles (TiO2 NPs) were successfully synthesized. The XRD pattern and FTIR spectra demonstrated the crystalline structure of TiO2 NPs and the presence of phenols, flavonoids and alkaloids in the extract. Further SEM revealed that TiO2 NPs has uniform structure and spherical in shape with their size ranged from 58 to 117 nm. Antibacterial activity of TiO2 NPs against methicillin-resistant Staphylococcus aureus (MRSA) and Vibrio cholerae (V. cholerae), provided the zone of inhibition of 33.9 ± 1.7 and 36.3 ± 1.9 mm, respectively at 100 μg/mL concentration. MIC of TiO2 NPs against MRSA and V. cholerae showed 84% and 87% inhibition at 180 μg/mL and 160 μg/mL respectively. Subsequently, the sub-MIC of V. cholerae demonstrated minimal or no impact on bacterial growth at concentration of 42.5 μg/mL concentration. In addition, TiO2 NPs exhibited their ability to inhibit the biofilm forming V. cholerae which caused distinct morphological and intercellular damages analysed using CLSM and TEM. The antioxidant properties of TiO2 NPs were demonstrated through TAA and DPPH assays and exposed its scavenging activity with IC50 value of 36.42 and 68.85 μg/mL which denotes its valuable antioxidant properties with potential health benefits. Importantly, the brine shrimp based lethality experiment yielded a low cytotoxic effect with 13% mortality at 100 μg/mL. In conclusion, the multifaceted attributes of C. serrulata mediated TiO2 NPs encompassed the antibacterial, antioxidant and anti-biofilm inhibition effects with low cytotoxicity in nature were highlighted in this study and proved the bioderived TiO2 NPs could be used as a promising agent for biomedical applications.

Rosmarinic Acid and Flavonoids of the Seagrass Zostera noltei: New Aspects on Their Quantification and Their Correlation with Sunlight Exposure

Seagrasses are plants adapted to the marine environment that inhabit shallow coastal waters, where they may be exposed to direct sunlight during low tides. These plants have photoprotection mechanisms, which could include the use of phenolic secondary metabolites. In this study, rosmarinic acid (RA) and the flavonoids of Zostera noltei from the Bay of Cadiz (Spain) have been analyzed, first to define suitable conditions of leaves (i.e., fresh, dried, or frozen) for quantitative analysis, and then to explore the potential correlation between the phenolic profile of the leaves and sunlight exposure using an in situ experimental approach. Compared with fresh leaves, the contents of RA and flavonoids were significantly lower in air-dried and freeze-dried leaves. Freezing caused highly variable effects on RA and did not affect to flavonoid levels. On the other hand, the content of RA was significantly higher in plants that emerged during low tides than in plants permanently submerged, while plants underneath an artificial UV filter experienced a progressive reduction in RA content. However, the major flavonoids did not show a clear response to sunlight exposure and were unresponsive to diminished UV incidence. The results showed a positive correlation of RA with direct sunlight and UV exposure of leaves, suggesting that this compound contributes to the photoprotection of Z. noltei.

Valorization of Posidonia oceanica biomass: Role on germination of cucumber and tomato seeds

Biostimulants are organic compounds from plant sources such as botanical extracts and bioactive substances that promote plant growth, enhance photosynthesis and increase crop quality. The accumulation of detached Posidonia oceanica leaves on coasts of the Mediterranean Sea results in economic problems, due to the rejection of the tourists who frequent the beaches in the summer months. However, it is a plant with high content of secondary metabolites that can be used in sustainable agriculture. In this study we investigated the physicochemical characterization of Posidonia oceanica extracts with three different solutions and their application in tomato and cucumber seeds germination. The results showed that the aqueous extract of Posidonia oceanica had a high concentration of macro and micronutrients, as well as secondary metabolites with bioactive activity. The aqueous extract had a beneficial effect on both leaf and root growth on tomato seeds, specifically, an increase of 76% for the relative root growth and 73% for the germination index was obtained with respect to the control using the sample with the intermediate dilution (POe0.5). In addition, the extracts did not show toxicity to either germination or growth of the tomato plant. As for cucumber seed germination, the improvement was less significant and did result in a phytotoxic effect on both germination and plant growth. The most diluted extract had better results on seed germination. Therefore, the application of aqueous extracts of Posidonia oceanica were suitable to be appropriate for tomato germination and in turn contribute to eliminate the lots of Posidonia oceanica remains recovered in summer months in Mediterranean beaches.

Phenolic chemistry of the seagrass Zostera marina Linnaeus: First assessment of geographic variability among populations on a broad spatial scale

The variability of the phenolic content of thirteen populations of Zostera marina L. (six narrow-leaved and seven wide-leaved ecotypes) from different geographical zones, i.e., Baltic Sea, Mediterranean, East and West Atlantic, and East Pacific coasts was evaluated. Depending on the location, three to five phenolic acids and nine to fourteen flavonoids were identified of which an undescribed flavonoid sulfate. The phenolic concentrations of the thirteen populations differ among countries and among sites within countries. However, the same individuals were found almost everywhere. Substantial phenolic concentrations were found at all study sites with the exception of Puck Bay (Baltic Sea). Some geographical differences in the flavonoid content were observed. The highest phenolic diversity was found with specimens from the French Atlantic coast and the lowest with the Northeastern American sample (Cape Cod, MA). Regardless of their leaf width, the content of phenolic compounds was found to be similar and mainly characterized by rosmarinic acid and luteolin 7,3'-disulfate. The results demonstrate that geographic origin influences the phenolic composition of Z. marina primarily in terms of concentration, but not in terms of individual compound identity, despite the large geographic scale and the contrasting climatic and environmental conditions associated with it. This work is the first study to consider the spatial variability of phenolic compounds for a seagrass species on a spatial scale covering four bioregions. This is also the first to compare the phenolic chemistry of the two ecotypes of Z. marina.

Small Molecule in situ Resin Capture - A Compound First Approach to Natural Product Discovery

Microbial natural products remain an important resource for drug discovery. Yet, commonly employed discovery techniques are plagued by the rediscovery of known compounds, the relatively few microbes that can be cultured, and laboratory growth conditions that do not elicit biosynthetic gene expression among myriad other challenges. Here we introduce a culture independent approach to natural product discovery that we call the Small Molecule In situ Resin Capture (SMIRC) technique. SMIRC exploits in situ environmental conditions to elicit compound production and represents a new approach to access poorly explored chemical space by capturing natural products directly from the environments in which they are produced. In contrast to traditional methods, this compound-first approach can capture structurally complex small molecules across all domains of life in a single deployment while relying on Nature to provide the complex and poorly understood environmental cues needed to elicit biosynthetic gene expression. We illustrate the effectiveness of SMIRC in marine habitats with the discovery of numerous new compounds and demonstrate that sufficient compound yields can be obtained for NMR-based structure assignment. Two new compound classes are reported including one novel carbon skeleton that possesses a functional group not previously observed among natural products and a second that possesses potent biological activity. We introduce expanded deployments, in situ cultivation, and metagenomics as methods to facilitate compound discovery, enhance yields, and link compounds to producing organisms. This compound first approach can provide unprecedented access to new natural product chemotypes with broad implications for drug discovery.

Pectin from Three Vietnamese Seagrasses: Isolation, Characterization, and Antioxidant Activity

This study focused on the isolation and structural characterization of pectin from three distinct species of Vietnamese seagrass including Enhalus acoroides, Thalassia hemprichii, and Halophila ovalis. The pectin yield obtained from Enhalus acoroides was the highest, corresponding to 24.15%, followed by those from Thalassia hemprichii (20.04%) and Halophila ovalis (19.14%). The physicochemical properties of pectin including total carbohydrate content, anhydrouronic acid (AUA) content, equivalent weight (EW), methoxyl content (MeO), and degree of esterification (DE) were determined using various analysis techniques. The pectin obtained from all three species were found to be low-methyl-esterified pectin, with the MeO content and DE for E. acoroides, T. hemprichii, and H. ovalis being 6.15% and 27.18%, 3.26% and 43.31%, and 4.65% and 33.25%, respectively. The average molecular weight (MW) of pectin was analyzed by size-exclusion chromatography. Pectin from T. hemprichii had the highest MW of 173.01 kDa, followed by pectin from E. acoroides, with a MW of 127.32 kDa, and that from H. ovalis, with a MW of 56.06 kDa. Furthermore, the pectins from all three seagrass species exhibited high antioxidant activity and might be promising as antioxidants.

The effect of warming on seagrass wasting disease depends on host genotypic identity and diversity

Temperature increases due to climate change have affected the distribution and severity of diseases in natural systems, causing outbreaks that can destroy host populations. Host identity, diversity, and the associated microbiome can affect host responses to both infection and temperature, but little is known about how they could function as important mediators of disease in altered thermal environments. We conducted an 8-week warming experiment to test the independent and interactive effects of warming, host genotypic identity, and host genotypic diversity on the prevalence and intensity of infections of seagrass (Zostera marina) by the wasting disease parasite (Labyrinthula zosterae). At elevated temperatures, we found that genotypically diverse host assemblages had reduced infection intensity, but not reduced prevalence, relative to less diverse assemblages. This dilution effect on parasite intensity was the result of both host composition effects as well as emergent properties of biodiversity. In contrast with the benefits of genotypic diversity under warming, diversity actually increased parasite intensity slightly in ambient temperatures. We found mixed support for the hypothesis that a growth-defense trade-off contributed to elevated disease intensity under warming. Changes in the abundance (but not composition) of a few taxa in the host microbiome were correlated with genotype-specific responses to wasting disease infections under warming, consistent with the emerging evidence linking changes in the host microbiome to the outcome of host-parasite interactions. This work emphasizes the context dependence of biodiversity-disease relationships and highlights the potential importance of interactions among biodiversity loss, climate change, and disease outbreaks in a key foundation species.

Carbon metabolism and bioavailability of dissolved organic carbon (DOC) fluxes in seagrass communities are altered under the presence of the tropical invasive alga Halimeda incrassata

Seagrass beds act as blue carbon sinks globally as they enhance the trapping of recalcitrant (i.e., low biodegradability) organic carbon in their sediments. Recent studies also show that the recalcitrant fraction of the dissolved organic carbon (DOC) pool in seawater has an important role as long-term carbon sequestration in oceans. Although seagrasses are known for the large amount of DOC they export, little attention has been given to its biodegradability, which ultimately determinates its fate in the coastal carbon cycle. In turn, invasive algae are a major global concern in seagrass ecosystems since they can deeply modify their structure and functions, which may affect carbon metabolism and DOC release. This work assesses how the presence of Halimeda incrassata, an invasive tropical calcareous macroalga, modifies carbon metabolism and DOC fluxes in invaded areas dominated by the seagrass Cymodocea nodosa. Our results show that stands with the presence of this seagrass (i.e., both monospecific and mixed meadow) had the highest production values, acting as high DOC producers in both winter (mainly of labile DOC; DOC_L) and summer (mainly as recalcitrant DOC; DOC_R). In contrast, monospecific H. incrassata beds exhibited low production values, and the presence of this macroalga (either as monospecific beds or mixed with C. nodosa) triggered the shift from a net DOC-producing-system in summer (mainly DOC_L) to a net DOC-consuming-system in winter. This work thus suggests that C. nodosa meadows have the potential to export a significant fraction of both labile and recalcitrant DOC, and that the spread of this invasive alga might decrease the C export capacity of seagrass meadows. Such shift would imply the reduction of a quick and efficient transfer of carbon and energy to higher trophic levels, and might reduce the blue carbon potential of seagrasses as dissolved form in the water column.

The fate of antibiotic resistance genes, microbial community, and potential pathogens in the maricultural sediment by live seaweeds and oxytetracycline

Three common seaweeds including Ulva fasciata, Codium cylindricum and Ishige okamurai were used for the remediation of maricultural wastewater and sediment in the presence/absence of trace level of oxytetracycline (OTC) in lab-scale experiments. Higher NO₃^--N and PO₄^3--P removal rates were achieved due to the presence of seaweeds, and trace OTC also had a positive effect on NO₃^--N removal. A slight variation of 2.10-2.15% were observed in the total relative abundances of antibiotic resistance genes (ARGs) of different sediment samples after one-month operation. However, the variation of ARGs profiles by the co-existence of different seaweeds and OTC was in the descending order of Ishige okamurai > Codium cylindricum > Ulva fasciata, which was in accordance with the variation of microbial hosts at genus level. The abundance of dominant tetracycline resistance genes promoted by the co-existence of different seaweeds and OTC in compared with the presence of single seaweed or OTC via metagenomic sequencing and qPCR analysis, and the co-existence of Ishige okamurai and OTC exhibited the largest impact. The potential pathogens were more sensitive to the co-existence of seaweed and OTC than single seaweeds. Meanwhile, a variety of ARGs were enriched in the pathogens, and the dominant pathogenic bacteria of Vibrio had 133 Vibrio species with 28 subtypes of ARGs. The variation of ARGs profiles in the sediment were strongly related with the dominant phyla Proteobacteria, Actinobacteria, Firmicutes, Planctomycetes and Cyanobacteria. Besides, Nitrate level exhibited more significant effect on ∑ARGs, ARGs resistant to vancomycin and streptogramin_a, while phosphate level exhibited more positively significant effect on ARGs resistant to fosmidomycin, ATFBT and cephalosporin.

Phenolic fingerprints of the Pacific seagrass Phyllospadixtorreyi - Structural characterization and quantification of undescribed flavonoid sulfates

Four undescribed flavonoid sulfates were isolated from Phyllospadix torreyi S. Watson foliar tissue. In addition, nine known flavonoid sulfates and three phenolic acids were isolated from the same extract, of which seven had never been reported for the genus Phyllospadix. Structural elucidation of individual phenolics was assigned using complementary informations from their spectral evidence (HPLC-DAD, LC-MS, NMR, and UV) and chemical behavior. The inter-annual variation in phenolic concentrations was determined by quantitative HPLC-DAD over a three-year period. The results showed a relative constancy of phenolic content over time and the high prevalence of flavonoid disulfates (70-90% of the total flavonoids detected). All samples were found dominated by the unreported nepetin 7, 3'-disulfate and 5-methoxyluteolin 7, 3'-disulfate, followed by luteolin 7, 3'-disulfate. Considering the economic potential of flavonoid sulfates in the pharmaceutical and nutraceutical segments, a sample of detrital leaves was also analyzed. The same phenolic pattern was found and the concentration of the individuals, although lower than in fresh material, makes this abundant biomass of interest for dietary and pharmaceutical applications.

Microbial Metabolites Beneficial to Plant Hosts Across Ecosystems

Plants are intimately connected with their associated microorganisms. Chemical interactions via natural products between plants and their microbial symbionts form an important aspect in host health and development, both in aquatic and terrestrial ecosystems. These interactions range from negative to beneficial for microbial symbionts as well as their hosts. Symbiotic microbes synchronize their metabolism with their hosts, thus suggesting a possible coevolution among them. Metabolites, synthesized from plants and microbes due to their association and coaction, supplement the already present metabolites, thus promoting plant growth, maintaining physiological status, and countering various biotic and abiotic stress factors. However, environmental changes, such as pollution and temperature variations, as well as anthropogenic-induced monoculture settings, have a significant influence on plant-associated microbial community and its interaction with the host. In this review, we put the prominent microbial metabolites participating in plant-microbe interactions in the natural terrestrial and aquatic ecosystems in a single perspective and have discussed commonalities and differences in these interactions for adaptation to surrounding environment and how environmental changes can alter the same. We also present the status and further possibilities of employing chemical interactions for environment remediation. Our review thus underlines the importance of ecosystem-driven functional adaptations of plant-microbe interactions in natural and anthropogenically influenced ecosystems and their possible applications.

Specialized compounds across ontogeny in the seagrass Posidonia oceanica

Differences in phenolic composition across different ontogenic stages can be crucial in determining the interaction outcomes between plants and their surrounding biotic environment. In seagrasses, specific phenolic compounds have rarely been analyzed and remain unexplored in ontogenic stages other than non-reproductive adults. Furthermore, it is generally accepted that plants would prioritize defense (e.g., through increased phenolic content) on tissues or stages that are critical for plant fitness but how this affects nutritional quality or plant resources has been scarcely explored. We analyzed how phenolic composition, N and C content and carbohydrate resources varied among different life stages (i.e. old and young leaves of reproductive and non-reproductive plants, and leaves of seedlings) in the seagrass Posidonia oceanica. We identified five phenolic compounds, whose structures were established as hydroxycinnamate esters of tartaric acid. Also, our results show that in all examined ontogenic stages phenolic compounds have the same qualitative composition but inflorescences exhibit higher contents than vegetative tissues. We did not find a reduction in stored resources in reproductive plants, pointing to some kind of compensatory mechanism in the production or storage of resources. In contrast, seedlings seemed to have less phenolic compounds than reproductive plants, perhaps due to limited resources available to allocate to phenolic production. Our results demonstrate how different ontogenic stages change their investment in specialized phenolic compounds prioritizing different functions according to the needs and limitations of that stage.

Seasonal variation of phenolic compounds in Zostera marina (Zosteraceae) from the Baltic Sea

Seasonal variations of phenolic compounds, in leaves of Zostera marina L. from the Baltic Sea near Kiel/Germany were investigated. Dominant compounds were mono- and disulfated flavonoids and phenylpropanoic acids, in particular luteolin 7,3'-O-disulfate and diosmetin 7-O-sulfate as well as rosmarinic acid, a dimeric phenylpropanoid. All detected sulfated flavones showed similar seasonal trends: there were two significant concentration peaks in June and November. Moreover, two geographically distinct flavonoid chemotypes were identified based on their respective main flavonoid; one chemotype was characterized by the prevalence of luteolin 7,3'-O-disulfate (German Baltic Sea), and the other by the prevalence of diosmetin 7-O-sulfate (Norwegian North Sea). Furthermore, an undescribed tetrameric phenylpropanoid, 7'',8''-didehydrosalvianolic acid B, was isolated and its structure was established by extensive NMR, MS, and CD experiments. This compound inhibited activity of Na⁺/K⁺-ATPase in the micro-molar range without any cytotoxic effects against human cancer and normal cells.

Antioxidant Bioactivity of Extracts from Beach Cast Leaves of Posidonia oceanica (L.) Delile

The marine environment is a generous source of biologically active compounds useful for human health. In 50 years, about 25,000 bioactive marine compounds have been identified, with an increase of 5% per year. Peculiar feature of algae and plants is the production of secondary metabolites, such as polyphenols, synthesized as a form of adaptation to environmental stress. Posidonia oceanica is a Mediterranean endemic and dominant seagrass and represents a biologically, ecologically and geologically important marine ecosystem. Within this study, methanolic and ethanolic extracts were generated from fresh and dried Posidonia oceanica leaves, with the aim to employ and valorize the beach cast leaves. The best yield and antioxidant activity (polyphenols content equal to 19.712 ± 0.496 mg GAE/g and DPPH IC50 of 0.090 µg/µL.) were recorded in 70% ethanol extracts (Gd-E4) obtained from leaves dried for two days at 60 °C and ground four times. HPLC analyses revealed the presence of polyphenols compounds (the most abundant of which was chicoric acid) with antioxidant and beneficial properties. Bioactive properties of the Gd-E4 extracts were evaluated in vitro using fibroblast cells line (HS-68), subjected to UV induced oxidative stress. Pre-treatment of cells with Gd-E4 extracts led to significant protection against oxidative stress and mortality associated with UV exposure, thus highlighting the beneficial properties of antioxidants compounds produced by these marine plants against photo damage, free radicals and associated negative cellular effects. Beach cast leaves selection, processing and extraction procedures, and the in vitro assay results suggested the potentiality of a sustainable approach for the biotechnological exploitation of this resource and could serve a model for other marine resources.

Molecular imaging of plant-microbe interactions on the Brachypodium seed surface

Plant growth-promoting rhizobacteria (PGPR) play a crucial role in biological control and pathogenic defense on and within plant tissues, however the mechanisms by which plants associate with PGPR to elicit such beneficial effects need further study. Here, we present time-of-flight secondary ion mass spectrometry (ToF-SIMS) imaging of Brachypodium distachyon (Brachypodium) seeds with and without exposure to two model PGPR, i.e., Gram-negative Pseudomonas fluorescens SBW25 (P.) and Gram-positive Arthrobacter chlorophenolicus A6 (A.). Delayed image extraction was used to image PGPR-treated seed sections to reveal morphological changes. ToF-SIMS spectral comparison, principal component analysis (PCA), and two-dimensional (2D) imaging show that the selected PGPR have different effects on the host seed surface, resulting in changes in chemical composition and morphology. Metabolite products and biomarkers, such as flavonoids, phenolic compounds, fatty acids, and indole-3-acetic acid (IAA), were identified on the PGPR-treated seed surfaces. These compounds have different distributions on the Brachypodium seed surface for the two PGPR, indicating that the different bacteria elicit distinct responses from the host. Our results illustrate that ToF-SIMS is an effective tool to study plant-microbe interactions and to provide insightful information with submicrometer lateral resolution of the chemical distributions associated with morphological features, potentially offering a new way to study the mechanisms underlying beneficial roles of PGPR.

The Gut Microbiota of Naturally Occurring and Laboratory Aquaculture Lytechinus variegatus Revealed Differences in the Community Composition, Taxonomic Co-Occurrence, and Predicted Functional Attributes

Sea urchins, in many instances, are collected from the wild, maintained in the laboratory aquaculture environment, and used as model animals for various scientific investigations. It has been increasingly evident that diet-driven dysbiosis of the gut microbiome could affect animal health and physiology, thereby impacting the outcome of the scientific studies. In this study, we compared the gut microbiome between naturally occurring (ENV) and formulated diet-fed laboratory aquaculture (LAB) sea urchin Lytechinus variegatus by amplicon sequencing of the V4 region of the 16S rRNA gene and bioinformatics tools. Overall, the ENV gut digesta had higher taxa richness with an abundance of Propionigenium, Photobacterium, Roseimarinus, and Flavobacteriales. In contrast, the LAB group revealed fewer taxa richness, but noticeable abundances of Arcobacter, Agarivorans, and Shewanella. However, Campylobacteraceae, primarily represented by Arcobacter spp., was commonly associated with the gut tissues of both ENV and LAB groups whereas the gut digesta had taxa from Gammaproteobacteria, particularly Vibrio spp. Similarly, the co-occurrence network displayed taxonomic organizations interconnected by Arcobacter and Vibrio as being the key taxa in gut tissues and gut digesta, respectively. Predicted functional analysis of the gut tissues microbiota of both ENV and LAB groups showed a higher trend in energy-related metabolisms, whereas amino acids, carbohydrate, and lipid metabolisms heightened in the gut digesta. This study provides an outlook of the laboratory-formulated diet-fed aquaculture L. variegatus gut microbiome and predicted metabolic profile as compared to the naturally occurring animals, which should be taken into consideration for consistency, reproducibility, and translatability of scientific studies.

Motility, biofilm formation and associated gene expression in Vibrio parahaemolyticus impaired by co-culture with live Ulva fasciata

AIMS

Vibrio parahaemolyticus is one of the most frequently occurred pathogens in mariculture. This study aimed to explore the mechanism of the impact of Ulva fasciata on the motility and biofilm formation of V. parahaemolyticus.

METHODS AND RESULTS

The inhibitory effect of U. fasciata on a V. parahaemolyticus, isolated from clam maricultural sediment, was examined by co-culture of them. The live U. fasciata significantly inhibited the swimming behaviour, twitching behaviour and biofilm formation of V. parahaemolyticus JF, with inhibition rates range of 2.48%-20.26%, 1.59%-39.18% and 28.3%-94.7% under different nitrate and phosphate levels, respectively. The results of transcriptome sequencing showed that 210 significantly differentially expressed genes (DEGs) were found in strain JF between the presence and absence of U. fasciata, including 90 upregulated genes and 120 downregulated genes. According to GO (Gene Ontology) function enrichment and KEGG (Kyoto Encyclopedia of Genes and Genomes) pathway analysis, the downregulated genes of JF were partially enriched in flagella assembly (fliC, fliK, fliG, fliN, fliH, fliI, fliJ and fliA), bacterial chemotaxis (mCP, cheB, cheW and cheY) and biofilm formation (fliA/σ²⁸ and eps), which explained the suppressed motility and biofilm formation of V. parahaemolyticus JF under U. fasciata stress.

CONCLUSIONS

Live U. fasciata significantly impaired the motility and biofilm formation of V. parahaemolyticus, which could occur in niches with either sufficient or inadequate nutrient (nitrate and phosphate) concentrations. The DEGs of V. parahaemolyticus modulated by U. fasciata were enriched mainly in the flagellar assembly, bacterial chemotaxis and biofilm pathways.

SIGNIFICANCE AND IMPACT OF THE STUDY

New information on how V. parahaemolyticus respond to U. fasciata regarding motility and adhesion behaviours, and the mechanism of that was firstly explored in this study. The results suggested that the seaweed U. fasciata has promising prospects as an environmentally friendly preventive measure to treat vibriosis in mariculture.

Molecular Networking Leveraging the Secondary Metabolomes Space of Halophila stipulaceae (Forsk.) Aschers. and Thalassia hemprichii (Ehrenb. ex Solms) Asch. in Tandem with Their Chemosystematics and Antidiabetic Potentials

The Red Sea is one of the most biodiverse aquatic ecosystems. Notably, seagrasses possess a crucial ecological significance. Among them are the two taxa Halophila stipulacea (Forsk.) Aschers., and Thalassia hemprichii (Ehrenb. ex Solms) Asch., which were formally ranked together with the genus Enhalus in three separate families. Nevertheless, they have been recently classified as three subfamilies within Hydrocharitaceae. The interest of this study is to explore their metabolic profiles through ultra-high-performance liquid chromatography-high-resolution mass spectrometry (UPLC-HRMS/MS) analysis in synergism with molecular networking and to assess their chemosystematics relationship. A total of 144 metabolites were annotated, encompassing phenolic acids, flavonoids, terpenoids, and lipids. Furthermore, three new phenolic acids; methoxy benzoic acid-O-sulphate (16), O-caffeoyl-O-hydroxyl dimethoxy benzoyl tartaric acid (26), dimethoxy benzoic acid-O-sulphate (30), a new flavanone glycoside; hexahydroxy-monomethoxy flavanone-O-glucoside (28), and a new steviol glycoside; rebaudioside-O-acetate (96) were tentatively described. Additionally, the evaluation of the antidiabetic potential of both taxa displayed an inherited higher activity of H. stipulaceae in alleviating the oxidative stress and dyslipidemia associated with diabetes. Hence, the current research significantly suggested Halophila, Thalassia, and Enhalus categorization in three different taxonomic ranks based on their intergeneric and interspecific relationship among them and supported the consideration of seagrasses in natural antidiabetic studies.

What drives putative bacterial pathogens removal within seagrass meadows?

To analyze the mechanism of bacterial pathogen removal in seagrass meadows, we compared bacterial pathogens abundance in trapped particles in different seagrass meadows under different intensities of human activities. We compared the particle deposition rates and abundances of bacterial pathogen in Thalassia hemprichii, Enhalus acoroides stands and adjacent unvegetated patches. The bacterial pathogens abundance was much higher in E. acoroides than in adjacent unvegetated patches, however, the trapped particles under T. hemprichii were lower than in nearby unvegetated areas with the exception of the pristine seagrass meadow. These results indicate that seagrass, at least E. acoroides, can remove bacterial pathogens by trapping particles. What is unknown, nevertheless, is how the trapped bacterial pathogens are removed by T. hemprichii. We put forward that antibacterial chemical compounds release from seagrass was stimulated by stress from human activities for inhibition of bacterial pathogen. This putative mechanism needs to be explored in future studies.

Preliminary study on the possible impact of Thalassodendron ciliatum (Forss.) den Hartog acidic polysaccharide fractions against TAA induced liver failure

The water-soluble acidic polysaccharide from Thalassodendron ciliatum (Forss.) den Hartog was successfully extracted, fractionated and purified. The phytochemical profile of the two water-soluble fractions (F1 and F2), were detected using different analytic techniques. GC-MS analysis revealed the presence of 22 saccharide. Acidic polysaccharide, galacturonic and glucuronic acid were the most abundant. Moreover, paper chromatography and electrophoresis also performed as a preliminary chemical characterization of the polymer. The hepatoprotective activity of the fractions against thioacetamide (TAA) induced liver failure; antioxidant potential and preliminary immunomodulatory activity were assigned in-vivo. The results revealed a potent competence to improve the liver function profile (ALT, AST, total bilirubin, total glyceride, etc.) and a remarkable improvement in liver architecture in comparison to the challenged intoxicated groups. Moreover, they showed high anti-oxidative properties and a promising immunomodulatory influence via Il6. These findings provide new insight into the possible role of polysaccharide purified two fractions in the treatment of acute liver injury.

Variation in Phenolic Chemistry in Zostera marina Seagrass Along Environmental Gradients

Chemical ecology has been suggested as a less time-consuming and more cost-efficient monitoring tool of seagrass ecosystems than traditional methods. Phenolic chemistry in Zostera marina samples was analyzed against latitude, sea depth, sample position within a seagrass meadow (periphery or center) and wave exposure. Multivariate data analysis showed that rosmarinic acid correlated moderately positively with depth, while the flavonoids had an overall strong negative correlation with increasing depth—possibly reflecting lack of stress-induced conditions with increasing depth, rather than a different response to light conditions. At a molecular level, the flavonoids were separated into two groups; one group is well described by the variables of depth and wave exposure, and the other group that was not well described by these variables—the latter may reflect biosynthetic dependencies or other unrevealed factors. A higher flavonoid/rosmarinic acid ratio was seen in the periphery of a seagrass meadow, while the contrary ratio was seen in the center. This may reflect higher plant stress in the periphery of a meadow, and the flavonoid/rosmarinic acid ratio may provide a possible molecular index of seagrass ecosystem health. Further studies are needed before the full potential of using variation in phenolic chemistry as a seagrass ecosystem monitoring tool is established.

The Seagrass Holobiont: What We Know and What We Still Need to Disclose for Its Possible Use as an Ecological Indicator

Microbes and seagrass establish symbiotic relationships constituting a functional unit called the holobiont that reacts as a whole to environmental changes. Recent studies have shown that the seagrass microbial associated community varies according to host species, environmental conditions and the host’s health status, suggesting that the microbial communities respond rapidly to environmental disturbances and changes. These changes, dynamics of which are still far from being clear, could represent a sensitive monitoring tool and ecological indicator to detect early stages of seagrass stress. In this review, the state of art on seagrass holobiont is discussed in this perspective, with the aim of disentangling the influence of different factors in shaping it. As an example, we expand on the widely studied Halophila stipulacea’s associated microbial community, highlighting the changing and the constant components of the associated microbes, in different environmental conditions. These studies represent a pivotal contribution to understanding the holobiont’s dynamics and variability pattern, and to the potential development of ecological/ecotoxicological indices. The influences of the host’s physiological and environmental status in changing the seagrass holobiont, alongside the bioinformatic tools for data analysis, are key topics that need to be deepened, in order to use the seagrass-microbial interactions as a source of ecological information.

Marine Seagrass Extract of Thalassia testudinum Suppresses Colorectal Tumor Growth, Motility and Angiogenesis by Autophagic Stress and Immunogenic Cell Death Pathways

Marine plants have become an inexhaustible reservoir of new phytopharmaceuticals for cancer treatment. We demonstrate in vitro/in vivo antitumor efficacy of a standardized polyphenol extract from the marine angiosperm Thalassia testudinum (TTE) in colon tumor cell lines (RKO, SW480, and CT26) and a syngeneic allograft murine colorectal cancer model. MTT assays revealed a dose-dependent decrease of cell viability of RKO, CT26, and SW480 cells upon TTE treatment with IC₅₀ values of, respectively, 175, 115, and 60 μg/mL. Furthermore, TTE significantly prevented basal and bFGF-induced angiogenesis in the chicken chorioallantoic membrane angiogenesis assay. In addition, TTE suppressed bFGF-induced migration of endothelial cells in a wound closure assay. Finally, TTE treatment abrogated CT26 colorectal cancer growth and increased overall organism survival in a syngeneic murine allograft model. Corresponding transcriptome profiling and pathway analysis allowed for the identification of the mechanism of action for the antitumor effects of TTE. In line with our in vitro/in vivo results, TTE treatment triggers ATF4-P53-NFκB specific gene expression and autophagy stress pathways. This results in suppression of colon cancer cell growth, cell motility, and angiogenesis pathways in vitro and in addition promotes antitumor immunogenic cell death in vivo.

In Vitro Evaluation of Antioxidant Potential of the Invasive Seagrass Halophila stipulacea

Marine organisms with fast growth rates and great biological adaptive capacity might have biotechnological interests, since ecological competitiveness might rely on enhanced physiological or biochemical processes’ capability promoting protection, defense, or repair intracellular damages. The invasive seagrass Halophila stipulacea, a non-indigenous species widespread in the Mediterranean Sea, belongs to this category. This is the premise to investigate the biotechnological interest of this species. In this study, we investigated the antioxidant activity in vitro, both in scavenging reactive oxygen species and in repairing damages from oxidative stress on the fibroblast human cell line WI-38. Together with the biochemical analysis, the antioxidant activity was characterized by the study of the expression of oxidative stress gene in WI-38 cells in presence or absence of the H. stipulacea extract. Concomitantly, the pigment pool of the extracts, as well as their macromolecular composition was characterized. This study was done separately on mature and young leaves. Results indicated that mature leaves exerted a great activity in scavenging reactive oxygen species and repairing damages from oxidative stress in the WI-38 cell line. This activity was paralleled to an enhanced carotenoids content in the mature leaf extracts and a higher carbohydrate contribution to organic matter. Our results suggest a potential of the old leaves of H. stipulacea as oxidative stress damage protecting or repair agents in fibroblast cell lines. This study paves the way to transmute the invasive H. stipulacea environmental threat in goods for human health.

The Cell Wall of Seagrasses: Fascinating, Peculiar and a Blank Canvas for Future Research

Seegrasses are a polyphyletic group of angiosperm plants, which evolved from early monocotyledonous land plants and returned to the marine environment around 140 million years ago. Today, seagrasses comprise the five families Zosteraceae, Hydrocharitaceae, Posidoniaceae, Cymodoceaceae, and Ruppiaceae and form important coastal ecosystems worldwide. Despite of this ecological importance, the existing literature on adaption of these angiosperms to the marine environment and especially their cell wall composition is limited up to now. A unique feature described for some seagrasses is the occurrence of polyanionic, low-methylated pectins mainly composed of galacturonic acid and apiose (apiogalacturonans). Furthermore, sulfated galactans have been detected in some species. Recently, arabinogalactan-proteins (AGPs), highly glycosylated proteins of the cell wall of land plants, have been isolated for the first time from a seagrass of the baltic sea. Obviously, seagrass cell walls are characterized by new combinations of structural polysaccharide and glycoprotein elements known from macroalgae and angiosperm land plants. In this review, current knowledge on cell walls of seagrasses is summarized and suggestions for future investigations are given.

Bioactive Properties of Marine Phenolics

Phenolic compounds from marine organisms are far less studied than those from terrestrial sources since their structural diversity and variability require powerful analytical tools. However, both their biological relevance and potential properties make them an attractive group deserving increasing scientific interest. The use of efficient extraction and, in some cases, purification techniques can provide novel bioactives useful for food, nutraceutical, cosmeceutical and pharmaceutical applications. The bioactivity of marine phenolics is the consequence of their enzyme inhibitory effect and antimicrobial, antiviral, anticancer, antidiabetic, antioxidant, or anti-inflammatory activities. This review presents a survey of the major types of phenolic compounds found in marine sources, as well as their reputed effect in relation to the occurrence of dietary and lifestyle-related diseases, notably type 2 diabetes mellitus, obesity, metabolic syndrome, cancer and Alzheimer's disease. In addition, the influence of marine phenolics on gut microbiota and other pathologies is also addressed.

The Microbiome of Posidonia oceanica Seagrass Leaves Can Be Dominated by Planctomycetes

Seagrass meadows are ubiquitous, fragile and endangered marine habitats, which serve as fish breeding grounds, stabilize ocean floor substrates, retain nutrients and serve as important carbon sinks, counteracting climate change. In the Mediterranean Sea, seagrass meadows are mostly formed by the slow-growing endemic plant Posidonia oceanica (Neptune grass), which is endangered by global warming and recreational motorboating. Despite its importance, surprisingly little is known about the leaf surface microbiome of P. oceanica. Using amplicon sequencing, we here show that species belonging to the phylum Planctomycetes can dominate the biofilms of young and aged P. oceanica leaves. Application of selective cultivation techniques allowed for the isolation of two novel planctomycetal strains belonging to two yet uncharacterized genera.

Natural Products, Traditional Uses and Pharmacological Activities of the Genus Biebersteinia (Biebersteiniaceae)

Medicinal plants have been known as a rich source of natural products (NPs). Due to their diverse chemical structures and remarkable pharmacological activities, NPs are regarded as important repertoires for drug discovery and development. Biebersteinia plant species belong to the Biebersteiniaceae family, and have been used in folk medicines in China and Iran for ages. However, the chemical properties, bioactivities and modes of action of the NPs produced by medicinal Biebersteinia species are poorly understood despite the fact that there are only four known Biebersteinia species worldwide. Here, we reviewed the chemical classifications and diversity of the various NPs found in the four known Biebersteinia species. We found that the major chemical categories in these plants include flavonoids, alkaloids, phenylpropanoids, terpenoids, essential oils and fatty acids. We also discussed the anti-inflammatory, analgesic, antibacterial, antioxidant, antihypertensive and hypoglycemic effects of the four Biebersteinia species. We believe that the present review will facilitate the exploration of traditional uses and pharmacological properties of Biebersteinia species, extraction of the NPs and elucidation of their molecular mechanisms, as well as the development of novel drugs based on the reported properties and mode-of-action.

A halo of reduced dinoflagellate abundances in and around eelgrass beds

Seagrass beds provide a variety of ecosystem services, both within and outside the bounds of the habitat itself. Here we use environmental DNA (eDNA) amplicons to analyze a broad cross-section of taxa from ecological communities in and immediately surrounding eelgrass (Zostera marina). Sampling seawater along transects extending alongshore outward from eelgrass beds, we demonstrate that eDNA provides meter-scale resolution of communities in the field. We evaluate eDNA abundance indices for 13 major phylogenetic groups of marine and estuarine taxa along these transects, finding highly local changes linked with proximity to Z. marina for a diverse group of dinoflagellates, and for no other group of taxa. Eelgrass habitat is consistently associated with dramatic reductions in dinoflagellate abundance both within the contiguous beds and for at least 15 m outside, relative to nearby sites without eelgrass. These results are consistent with the hypothesis that eelgrass-associated communities have allelopathic effects on dinoflagellates, and that these effects can extend in a halo beyond the bounds of the contiguous beds. Because many dinoflagellates are capable of forming harmful algal blooms (HABs) toxic to humans and other animal species, the apparent salutary effect of eelgrass habitat on neighboring waters has important implications for public health as well as shellfish aquaculture and harvesting.

Phenolic Extract of Seagrass, Halophila ovalis Activates Intrinsic Pathway of Apoptosis in Human Breast Cancer (MCF-7) Cells

The marine ecosystem is considered as a treasure of numerous novel biologically active molecules. We investigated the anticancer potential of the phenolic extract of Halophila ovalis in breast cancer (MCF-7) cells and characterized the possible underlying molecular mechanism. The phenolic extract (5 µl) of H. ovalis effectively inhibited the growth of MCF-7 cells. The results of DAPI staining indicated that this phenolic extract potently induces apoptosis in MCF-7 cells which was observed by increased chromatin condensation in the treated cells. An increased expression of the active fragments of an executioner caspase, caspase 3 in phenolic extract-treated MCF-7 cells further confirms this apoptosis induction. In consequence, the loss of mitochondrial membrane potential was noticed in treated cells. The protein expression analyzes show decreased expression of the anti-apoptotic protein, Bcl-2, and DNA repair enzyme, PARP in treated cells indicating the probable molecular targets of apoptosis. Further, the phenolic extract of H. ovalis blocked the antioxidant defense system in MCF-7 cells by down-regulating the protein expression of a major transcription factor, Nrf-2 and regulatory antioxidant enzymes, SOD-2 and HO-1. These results show the presence of chemopreventive compound(s) in the phenolic extract, which offers a platform for future studies to identify the active principles.

The seagrass holobiont: understanding seagrass-bacteria interactions and their role in seagrass ecosystem functioning

This review shows that the presence of seagrass microbial community is critical for the development of seagrasses; from seed germination, through to phytohormone production and enhanced nutrient availability, and defence against pathogens and saprophytes. The tight seagrass-bacterial relationship highlighted in this review supports the existence of a seagrass holobiont and adds to the growing evidence for the importance of marine eukaryotic microorganisms in sustaining vital ecosystems. Incorporating a micro-scale view on seagrass ecosystems substantially expands our understanding of ecosystem functioning and may have significant implications for future seagrass management and mitigation against human disturbance.

Response of foundation macrophytes to near-natural simulated marine heatwaves

Marine heatwaves have been observed worldwide and are expected to increase in both frequency and intensity due to climate change. Such events may cause ecosystem reconfigurations arising from species range contraction or redistribution, with ecological, economic and social implications. Macrophytes such as the brown seaweed Fucus vesiculosus and the seagrass Zostera marina are foundation species in many coastal ecosystems of the temperate northern hemisphere. Hence, their response to extreme events can potentially determine the fate of associated ecosystems. Macrophyte functioning is intimately linked to the maintenance of photosynthesis, growth and reproduction, and resistance against pathogens, epibionts and grazers. We investigated morphological, physiological, pathological and chemical defence responses of western Baltic Sea F. vesiculosus and Z. marina populations to simulated near-natural marine heatwaves. Along with (a) the control, which constituted no heatwave but natural stochastic temperature variability (0HW), two treatments were applied: (b) two late-spring heatwaves (June, July) followed by a summer heatwave (August; 3HW) and (c) a summer heatwave only (1HW). The 3HW treatment was applied to test whether preconditioning events can modulate the potential sensitivity to the summer heatwave. Despite the variety of responses measured in both species, only Z. marina growth was impaired by the accumulative heat stress imposed by the 3HW treatment. Photosynthetic rate, however, remained high after the last heatwave indicating potential for recovery. Only epibacterial abundance was significantly affected in F. vesiculosus. Hence both macrophytes, and in particular F. vesiculosus, seem to be fairly tolerant to short-term marine heatwaves at least at the intensities applied in this experiment (up to 5°C above mean temperature over a period of 9 days). This may partly be due to the fact that F. vesiculosus grows in a highly variable environment, and may have a high phenotypic plasticity.

Ecological Function of Phenolic Compounds from Mediterranean Fucoid Algae and Seagrasses: An Overview on the Genus Cystoseira sensu lato and Posidonia oceanica (L.) Delile

Biodiversity is undergoing rapid and worrying changes, partially driven by anthropogenic activities. Human impacts and climate change (e.g., increasing temperature and ocean acidification), which act at different spatial scales, represent the most serious threats to biodiversity and ecosystem structure and function. In the Mediterranean Sea, complex systems such as fucoid algae and seagrasses, characterized by a high associated biodiversity, are regularly exposed to natural and anthropogenic pressures. These systems, particularly sensitive to a variety of stressors, evolved several physiological and biochemical traits as a response to the different pressures which they are subjected to. For instance, they produce a huge quantity of secondary metabolites such as phenolic compounds, to adapt to different environmental stressors and to defend themselves from biological pressures. These natural products are receiving increasing attention due to their possible applications in a wide range of industrial sectors. In this paper we provide an overview on the ecological role of phenolic compounds from the genus Cystoseira sensu lato and Posidonia oceanica (L.) Delile, also highlighting their potential use as ecological biomarkers.

The Suitability of Fishes as Models for Studying Appetitive Behavior in Vertebrates

Fish have proven to be valuable models in the study of the endocrine control of appetite in response to peripheral signals of energetic and nutritional status. In parallel, a growing body of literature points to the importance of sensory experiences as factors affecting food choice in fish, with a special focus on visual and chemical signals allowing discrimination of potential foods within a 3D environment. Accordingly, waterborne compounds, such as monosaccharides or amino acids, are regarded as the main "olfactory" cues driving fish alimentary behavior. However, we recently suggested that hydrophobic molecules also allow food identification in aquatic environments and that fish actually explore a larger variety of chemosensory cues, including the olfactory/volatile compounds, when determining food palatability. In this study, we show that both homeostatic and chemosensory mechanisms involved in food intake are highly conserved in vertebrates and that the chemosensory world of fish is less different from that of terrestrial mammals than commonly thought. As a result, we support a more integrated and synthetic view of the mechanisms of chemical communication in both terrestrial and aquatic systems, which could help to ensure greater translatability of the fish models, such as the zebrafish (Danio rerio), the turquoise killifish (Nothobranchius furzeri), the goldfish (Carassius auratus), or the Japanese medaka fish (Oryzias latipes) to terrestrial vertebrates when approaching complex dynamic patterns in alimentary behavior.

Chemical Defence of a Seagrass against Microfoulers and Its Seasonal Dynamics

In marine environments bacterial microfoulers are an important determinant for the settlement of algal and animal macrofoulers. At the same time fouling is usually subject to seasonal fluctuation. Additionally, the seagrass Zostera marina is prone to microfouling, although this marine spermatophyte is known to be chemically defended against bacterial settlers. Spermatophytes are often capable of induced or activated defences against biological enemies such as pathogens or herbivores, but it is still unknown whether they can fine-tune their antifouling-defence according to settlement pressure. We therefore assessed the seasonality of bacterial settlement pressure, defence against microsettlers and concentrations of a previously identified defence compound, rosmarinic acid, on surfaces of Z. marina. All examined variables peaked in summer, while they tended to be lower in spring and autumn. The seasonality of defence activity and rosmarinic acid surface concentration was positively correlated with the seasonal fluctuation of fouling pressure, which suggests that Z. marina can adjust its defence level to the relatively high bacterial fouling pressure in summer. Besides of biotic factors the seasonal change of environmental factors, such as nitrogen supply, and in particular temperature, also affected the defence level, either directly or through indirect effects on the microbial settlers.

Surface chemical defence of the eelgrass Zostera marina against microbial foulers

Plants rely on both mechanical and chemical defence mechanisms to protect their surfaces against microorganisms. The recently completed genome of the eelgrass Zostera marina, a marine angiosperm with fundamental importance for coastal ecosystems, showed that its re-adaptation from land to the sea has led to the loss of essential genes (for chemical communication and defence) and structural features (stomata and thick cuticle) that are typical of terrestrial plants. This study was designed to understand the molecular nature of surface protection and fouling-control strategy of eelgrass against marine epiphytic yeasts. Different surface extraction methods and comparative metabolomics by tandem mass spectrometry (LC-MS/MS) were used for targeted and untargeted identification of the metabolite profiles of the leaf surface and the whole tissue extracts. Desorption electrospray ionization-imaging mass spectrometry (DESI-IMS) coupled with traditional bioassays revealed, for the first time, the unique spatial distribution of the eelgrass surface-associated phenolics and fatty acids, as well as their differential bioactivity against the growth and settlement of epiphytic yeasts. This study provides insights into the complex chemical defence system of the eelgrass leaf surface. It suggests that surface-associated metabolites modulate biotic interactions and provide chemical defence and structural protection to eelgrass in its marine environment.

Phenolic chemistry of the seagrass Zostera noltei Hornem. Part 1: First evidence of three infraspecific flavonoid chemotypes in three distinctive geographical regions

The flavonoid content of Zostera noltei leaves was investigated over a broad spatial scale using chromatographic and spectroscopic techniques (HPLC-DAD, LC/MS and NMR). Samples were collected at fifteen localities covering Mediterranean Sea and NE Atlantic coast, and representative of three types of coastal ecosystems: mesotidal bays, coastal lagoons, and open-sea. Three geographically distinct flavonoid chemotypes were identified on the basis of their respective major compound. One is characterized by apigenin 7-sulfate (Eastern part of Gulf of Cadiz), one by diosmetin 7-sulfate (French Atlantic coast and Mediterranean Sea), and the third contained similar quantities of the above two compounds (Mauritania and South Portugal). Our results show that metabolomic profiling using a combination of analytical techniques is a tool of choice to characterize chemical phenotype accurately. This work emphasizes for the first time the spatial variability in the flavonoid chemistry of Z. noltei throughout Atlantic and Mediterranean range, and constitutes the first report of chemical races in the Zosteraceae family. This infraspecific chemical differentiation should be considered when dealing with the role of Z. noltei in coastal ecosystems or in the selection of the best population donor for Z. noltei beds restoration. Combined with molecular identification, phenolic fingerprinting might be helpful to elucidate the evolutionary history of Z. noltei.

Diversity and antagonistic potential of bacteria isolated from marine grass Halodule uninervis

The aim of this study was to isolate bacteria from sea grass, Halodule uninervis collected from the coastal area of Jeddah, Saudi Arabia and to screen them for antifungal and enzymatic activities. We have isolated 162 rhizo and endophytic bacteria from soil, roots, and leaves of the sea grass. Antifungal screening of isolated bacteria revealed 19 strains (11.7%) capable to inhibit growth of four pathogenic fungi, Pythium ultimum, Phytophthora capsici, pyricularia oryzae, and Rhizoctonia solani in an in vitro assay. Taxonomic and phylogenetic analyses on the basis of 16S rRNA gene sequence revealed 97-99.9% sequence identity to recognized species. Bacillus, Staphylococcus, Jeotgalicoccus, and Planococcus, within the Phylum Firmicutes, Kocuria, Arthrobacter, Ornithinimicrobium and Corynebacterium (Actinobacteria), Sulfitobacter, Roseivivax, Ruegeria (α-Proteobacteria), Moraxella, and Vibrio (γ-Proteobacteria), were isolated. Strains belong to Phylum Firmicutes remain dominant antagonistic bacteria in this study. Further hydrolytic enzyme production was determined for these antagonistic bacteria. Our results demonstrated that the sea grass represents an important source of diverse antagonistic bacteria capable of producing antifungal metabolite.

High Value-Added Biomolecules from Beach Waste of Marine Origin-Screening for Potential Candidates among Seagrass of the Cymodoceaceae Family

Background:

Detrital leaves from seagrass of the Cymodoceaceae family were assayed for biologically active molecules that have commercial as well as societal benefits.

Objective:

We focused on L-chiro-inositol, a very rare natural occurring cyclitol, and chicoric acid, a polyphenolic compound, in which both applications were found in the nutraceutical segment.

Method:

Six species of seagrass belonging to the genera Syringodium, Cymodocea and Halodule were collected from their native habitat. The L-chiro-inositol content of the crude aqueous extracts prepared from different batches of Cymodocea nodosa flotsam was measured by quantitative 1H-NMR spectroscopy. High concentrations were found with values ranging from 22.2 to 35.0 mg.g-1 plant dw. The presence of L-chiro-inositol in the tropical species C. rotundata, C. serrulata, Syringodium isoetifolium, and Halodule pinifolia was also characterized by qualitative NMR. The chicoric acid content of crude aqueous methanolic extracts prepared from C. rotundata, C. serrulata, S. isoetifolium, and Halodule pinifolia was determined by quantitative HPLC-DAD. The values found ranged from 0.39 to 6.15 mg.g-1 dry weight. Chicoric acid was unambiguously identified as the major phenolic in S. isoetifolium, and Halodule pinifolia, while it was found in mixture with flavonol derivatives in C. rotundata and C. serrulata. Flavonol derivatives are also of interest for their bioactivity.

Result:

Considering the demonstrated therapeutic applications of L-chiro-inositol and chicoric acid, their high value on the nutraceutical market, and their rare occurrence in the plant kingdom, their presence in Syringodium, Cymodocea and Halodule detrital leaves makes this abundant biomass of interest for dietary and pharmaceutical applications.

Conclusion:

These results show that there is a real potential for harvesting beachcast Cymodoceacea.

Characterization of Polyphenolic Content in the Aquatic Plants Ruppia cirrhosa and Ruppia maritima -A Source of Nutritional Natural Products

Herein, the polyphenolic content in extracts of Ruppia cirrhosa (Petagna) Grande and Ruppia maritima L.was fully characterized for the first time. High amounts of the main compound chicoric acid (CA) (≤30.2 ± 4.3 mg/g) were found in both Ruppia species. In addition, eight flavonoids, namely the 3-O-glucopyranosides and 3-O-galactopyranosides, as well as malonylated 3-O-glycosides of quercetin and isorhamnetin, were isolated and identified. The antioxidant activity of Ruppia cirrhosa extracts and isolated compounds was investigated spectrophotometrically by a 1,1-diphenyl-2-picrylhydrazyl (DPPH·) radical scavenging assay. IC50 values were 31.8-175.7 μg/mL for Ruppia cirrhosa extracts and 12.1-88.4 μg/mL for isolated flavonoids. Both individual and total phenolic and flavonoid content were quantified in crude extracts using analytical HPLC. The relative high amount of total flavonoids ranged from 5.9 to 14.7 mg/g in both species, with concentrations of individual flavonoids ranging from 0.4 to 2.9 mg/g dry weight. The content of chicoric acid was twofold more in Ruppia maritima than in Ruppia cirrhosa. Seasonal variation of the quantitative content in Ruppia cirrhosa was examined. Total flavonoid content ranged from 8.4 mg/g in October to 14.7 mg/g in August, whereas the highest concentration of chicoric acid was observed in March (29.2 mg/g).

Proteomic Contributions to Medicinal Plant Research: From Plant Metabolism to Pharmacological Action

Herbal medicine is a clinical practice of utilizing medicinal plant derivatives for therapeutic purposes. It has an enduring history worldwide and plays a significant role in the fight against various diseases. Herbal drug combinations often exhibit synergistic therapeutic action compared with single-constituent dosage, and can also enhance the cytotoxicity induced by chemotherapeutic drugs. To explore the mechanism underlying the pharmacological action of herbs, proteomic approaches have been applied to the physiology of medicinal plants and its effects on animals. This review article focuses on the existing proteomics-based medicinal plant research and discusses the following topics: (i) plant metabolic pathways that synthesize an array of bioactive compounds; (ii) pharmacological action of plants tested using in vivo and in vitro studies; and (iii) the application of proteomic approaches to indigenous plants with scarce sequence information. The accumulation of proteomic information in a biological or medicinal context may help in formulating the effective use of medicinal plants.