Variation in microbial populations and antibiotic resistance genes in mariculture sediments in the present of the seaweed Ulva fasciata and under selective pressure of oxytetracycline.

The widely distributed seaweed Ulva fasciata has nutrient absorption abilities and can be used in the bioremediation of polluted maricultural environments. This study explored microbial community and antibiotic resistance gene (ARG) variation in mariculture sediments in response to different trace levels (10, 100, and 500 µg L-1) of oxytetracycline (OTC) and the presence of Ulva fasciata. The increase in OTC level promoted nutrient (NO3_-N and PO43--P) removal mainly due to Ulva fasciata adsorption. The abundances of the Euryarchaeota and Planctomycetes phyla in sediments were positively related to the increase in OTC stress, while a negative correlation occurred for the Proteobacteria phylum via metagenomic analysis. Compared with the control system, the increase rates of total ARGs were 3.90%, 7.36% and 13.42% at the OTC levels of 10, 100 and 500 µg L-1, respectively. OTC stress mainly favoured the collateral enrichment of non-corresponding polypeptide and MLS ARGs, mainly due to the enrichment of the phyla Planctomycetes and Euryarchaeota by the synergistic effect of OTC and nutrients. The results of quantitative PCR with tetracycline resistance genes (TRGs) (tetO, tetT, tetPB, tetW and otrA) and a horizontal transfer gene (intl1) demonstrated that all of genes had much higher gene numbers in sediments after 3 months of OTC stress than in those without OTC stress, which was strongly related to the variation in the phyla Bacteroidetes, Gemmatimonadetes and Acidobacteria. The significant correlation between intl1 and the target TRGs is indicative of the important role of the horizontal transfer of integron-resistant genes in the spread of TRGs.

Physiological and metabolic responses to hypersalinity reveal interpopulation tolerance in the green macroalga Ulva compressa with different pollution histories.

There is scarce investigation addressing interpopulation tolerance responses to address the influence of a history of chronic stress exposure, as that occurring in polluted environments, in photoautotrophs. We evaluated ecophysiological (photosynthetic activity) and metabolic (oxidative stress and damage) responses of two populations of green macroalga Ulva compressa from polluted (Ventanas) and non-polluted (Cachagua) localions of central Chile, and exposed to controlled hypersalinity conditions of 32 (control), 42, 62 and 82 psu (practical salinity units) for 6 h, 48 h and 6 d. Both primary production (ETRmax) and photosynthetic efficiency (αETR) were generally higher in the population from Cachagua compared to Ventanas at all times and salinities. Moreover, at most experimental times and salinities the population from Ventanas had greater levels of H2O2 and lipid peroxidation that individuals from Cachagua. Total ascorbate was higher in the population of Cachagua than Ventanas at 42 and 82 psu after 6 and 48 h, respectively, while at 6 d concentrations were similar between both populations at all salinities. Total glutathione was greater in both populations after 6 h at all salinities, but at 48 h its concentrations were higher only in the population from Cachagua, a trend that was maintained at 6 d under 82 psu only. Reduced and oxidized ascorbate (ASC and DHA, respectively) and glutathione (GSH and GSSG, respectively) demonstrated similar patterns between U. compressa populations, with an increase oxidation with greater salinities but efficient recycling to maintain sufficient batch of ASC and GSH. When assessing the expression of antioxidant enzymes catalase (CAT), superoxide dismutase (SOD) and dehydroascorbate reductase (DHAR), while the population of Ventanas displayed a general trend of upregulation with increasing salinities along the experiments, U. compressa from Cachagua revealed patterns of downregulation. Results demonstrated that although both populations were still viable after the applied hypersalinities during all experimental times, biological performance was usually more affected in the population from the Ventanas than Cachagua, likely due to a depressed baseline metabolism after a long history of exposition to environmental pollution.

Copper-induced concomitant increases in photosynthesis, respiration, and C, N and S assimilation revealed by transcriptomic analyses in Ulva compressa (Chlorophyta).

BACKGROUND: The marine alga Ulva compressa is the dominant species in copper-polluted coastal areas in northern Chile. It has been shown that the alga tolerates micromolar concentrations of copper and accumulates copper at the intracellular level. Transcriptomic analyses were performed using total RNA of the alga cultivated with 10 µ M copper for 0, 1, 3 and 5 days using RNA-seq in order to identify processes involved in copper tolerance. RESULTS: The levels of transcripts encoding proteins belonging to Light Harvesting Complex II (LHCII), photosystem II (PSII), cytochrome b6f, PSI, LHCI, ATP synthase and proteins involved in repair of PSII and protection of PSI were increased in the alga cultivated with copper. In addition, the level of transcripts encoding proteins of mitochondrial electron transport chain, ATP synthase, and enzymes involved in C, N and S assimilation were also enhanced. The higher percentages of increase in the level of transcripts were mainly observed at days 3 and 5. In contrast, transcripts involved protein synthesis and degradation, signal transduction, and replication and DNA repair, were decreased. In addition, net photosynthesis and respiration increased in the alga cultivated with copper, mainly at days 1 to 3. Furthermore, the activities of enzymes involved in C, N and S assimilation, rubisco, glutamine synthase and cysteine synthase, respectively, were also increased, mainly at days 1 and 3. CONCLUSIONS: The marine alga U. compressa tolerates copper excess through a concomitant increase in expression of proteins involved in photosynthesis, respiration, and C, N and S assimilation, which represents an exceptional mechanism of copper tolerance.

Differential Photosynthetic Response of a Green Tide Alga Ulva linza to Ultraviolet Radiation, Under Short- and Long-term Ocean Acidification Regimes.

Both ocean acidification (OA) and solar ultraviolet (UV) radiation can bring about changes in macroalgal physiological performance. However, macroalgal responses to UV radiation when acclimatized to OA under different time scales are rare. Here, we investigate the response of Ulva linza, a green tide alga, to UV radiation in the form of photosynthetically active radiation (PAR) or PAB (PAR+UVA+UVB) radiation. Radiation exposures were assessed following long-term (from spore to adult stage, 1 month) and short-term (adult stage, 1 week) OA treatments. Results showed that increased CO2 decreased the damage rate (k) and repair rate (r) of thalli grown under short-term OA conditions with PAB treatment, the ratio of r:k was not altered. Following long-term OA conditions, r was not affected, although k was increased in thalli following PAB treatment, resulting in a reduced ratio of r:k. The relative level of UV inhibition increased and UV-absorbing compounds decreased when algae were cultured under long-term OA conditions. The recovery rate of thalli was enhanced when grown under long-term OA after UV radiation treatment. These results show that blooming algae may be more sensitive to UV radiation in marine environments, but it can develop effective mechanisms to offset the negative effects, reflecting acclimation to long-term OA conditions.

Safety and quality of the green tide algal species Ulva prolifera for option of human consumption: A nutrition and contamination study.

This study sampled U. prolifera and surface seawater from the same locations where green tide broke out in the southern Yellow Sea, in both the year 2016 and 2017. The revealed nutritive components of U. prolifera samples characterized U. prolifera as a high-protein, high-Fe, high ratio of unsaturated lipid acids and low-fat seaweed food, with an ideal ratio of essential and nonessential amino acids. The concentrations and health risk assessment of major micropollutants (heavy metals, pesticides and polycyclic aromatic hydrocarbon (PAHs)) in U. prolifera were also analyzed, respectively. The results showed that the Target Hazard Quotient values of five heavy metals (<1.0 × 10-1) and the total hazard index of 13 pesticides (<1.5 × 10-8) were lower than the unity, respectively, and the incremental lifetime cancer risk values of PAHs (<7.4 × 10-7) were lower than the USEPA limit (1.0 × 10-6). It suggested that consuming U. prolifera is safe as a food-source option, with PAHs causing relatively higher risks. PAHs from the sites closer to the shore were also found more originated from pyrolysis. We further confirmed the PAH congeners were partly in equilibrium between seawater and U. prolifera. It suggested the possibility that the food safety-risk turned to be above the USEPA limit was not high regardless of the sample collecting time. However, the sources of PAHs and their contributions to the accumulation in U. prolifera need further investigation. This study favored that U. prolifera of the green tide from the southern Yellow Sea has a potential for a nutritious-food production.

Organic and inorganic nano-Fe3O4: Alga Ulva flexuosa-based synthesis, antimicrobial effects and acute toxicity to briny water rotifer Brachionus rotundiformis.

Following the recent progress in magnetic nanotechnology, concern over the optimal benefits and potential risks of iron oxide nanoparticles (Fe NPs), has increased. Hence, to minimize the negative impacts of inorganic Fe NPs, we report the phyco-synthesis and characterization of superparamagnetic Fe3O4 NPs via reduction of ferric/ferrous chloride solution (2:1 M ratio; 88 °C) with green macroalga, Ulva flexuosa (wulfen) J.Agardh aqueous extract. The biogenic process is clean, eco-friendly, rapid, and facile to handle. These green fabricated magnetite NPs are characterized by Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD), transmission electron microscopy (TEM), field emission scanning electron microscopy (FESEM), thermogravimetric analysis (TGA), particle size analysers (PSA), zeta potential (ZP) measurement, and vibrating sample magnetometry (VSM) techniques. The results confirmed that the cubo-spherical, polydisperse of biosynthesized Fe3O4 NPs with an average diameter of 12.3 nm was formed. The antagonistic effects of algal extract, chemo-route and U. flexuosa-derived Fe3O4 MgNPs on selective human pathogenic microbes (i.e. n = 11) resulted in strong antibacterial and moderate antifungal activity. The comparative toxic and reproductive effects of the chemo- and bio-routes of Fe3O4-MgNPs against rotifer B. rotundiformis exhibited low acute toxicity with a lower inducing effect of biogenic nano-magnetite on reduction rotifer reproductive rate than its chemogenic counterpart. In view of the nanoecotoxicity, though the current study covered a wide range of exposure concentrations (10-500 mg/L) of organic and inorganic nano sizes of Fe3O4 in brackish water rotifer, a biotoxicity assay at higher dosage or a comprehensive risk assessment in different aqua-organisms is recommended.

In vitro amoebicidal and antioxidant activities of some Tunisian seaweeds.

Free-living amoebae of genus Acanthamoeba are opportunistic pathogens widely distributed in the environment, and are the causative agents of several humans' infections, such as Acanthamoeba keratitis, Granulomatous Amoebic Encephalitis and also disseminated infections. The existence of the cyst stage complicates Acanthamoeba therapy as it is highly resistant to antibiotics and physical agents. All these facts reinforced the necessity to find and develop an effective therapy against Acanthamoeba infections. In the present study, we are interested to several seaweeds species collected from the Tunisian coasts and belonging to the 3 phyla (brown, green and red algae). The aim was to quantify the Total Phenolic Compounds in different organic extract, to evaluate antioxidant capacity (DPPH and ABTS) and to study the antiprotozoal activity against A. castellanii Neff. The parasites have been inhibited by all extracts with an IC50 ranged from 52,3±1.8 µg/mL for ethyl acetate extract, to 134,6±0.7 µg/mL for the hexanic one for the various species studied.

Vulnerability and acclimation to increased UVB radiation in three intertidal macroalgae of different morpho-functional groups.

The vulnerability and acclimation to increased UVB radiation in three macroalgae of different morpho-functional groups collected in the Mediterranean coastal waters were evaluated. The algae were submitted for 7 days to increased (PAB+) and decreased (PAB-) UVB radiation. The thickness and morphology influenced the response to increased UVB radiation, being Cystoseira tamariscifolia the less vulnerable algae followed by Ellisolandia elongata. The highest resistance to increased UVB radiation in C. tamariscifolia was related to the accumulation of polyphenols and high antioxidant activity, whereas E. elongata was due to its high reflectance. Finally, Ulva rigida suffered the highest photoinhibition under PAB+ culture. The latest species presented 10 times lower polyphenol content and antioxidant activity than C. tamariscifolia. The three species showed different acclimation patterns to the changes of UVB radiation related to the morphology, photosynthetic activity, accumulation of photoprotectors and antioxidant activities. The ecological implications of the UVB variations on macroalgae are discussed.

Slippery liquid-infused porous surfaces showing marine antibiofouling properties.

Marine biofouling is a longstanding problem because of the constant challenges placed by various fouling species and increasingly restricted environmental regulations for antifouling coatings. Novel nonbiocidal strategies to control biofouling will necessitate a multifunctional approach to coating design. Here we show that slippery liquid-infused porous surfaces (SLIPSs) provide another possible strategy to obtaining promising antifouling coatings. Microporous butyl methacrylate-ethylene dimethacrylate (BMA-EDMA) surfaces are prepared via UV-initiated free-radical polymerization. Subsequent infusion of fluorocarbon lubricants (Krytox103, Krytox100, and Fluorinert FC-70) into the porous microtexture results in liquid-repellent slippery surfaces. To study the interaction with marine fouling organisms, settlement of zoospores of the alga Ulva linza and cypris larvae of the barnacle Balanus amphitrite is tested in laboratory assays. BMA-EDMA surfaces infused with Krytox103 and Krytox100 exhibit remarkable inhibition of settlement (attachment) of both spores and cyprids to a level comparable to that of a poly(ethylene glycol) (PEG)-terminated self-assembled monolayer. In addition, the adhesion strength of sporelings (young plants) of U. linza is reduced for BMA-EDMA surfaces infused with Krytox103 and Krytox100 compared to pristine (noninfused) BMA-EDMA and BMA-EDMA infused with Fluorinert FC-70. Immersion tests suggest a correlation between the stability of slippery coatings in artificial seawater and fouling resistance efficacy. The results indicate great potential for the application of this concept in fouling-resistant marine coatings.

Physiological and biochemical responses of Ulva prolifera and Ulva linza to cadmium stress.

Responses of Ulva prolifera and Ulva linza to Cd(2+) stress were studied. We found that the relative growth rate (RGR), Fv/Fm, and actual photochemical efficiency of PSII (Yield) of two Ulvaspecies were decreased under Cd(2+) treatments, and these reductions were greater in U. prolifera than in U. linza. U. prolifera accumulated more cadmium than U. linza under Cd(2+) stress. While U. linza showed positive osmotic adjustment ability (OAA) at a wider Cd(2+) range than U. prolifera. U. linza had greater contents of N, P, Na(+), K(+), and amino acids than U. prolifera. A range of parameters (concentrations of cadmium, Ca(2+), N, P, K(+), Cl(-), free amino acids (FAAs), proline, organic acids and soluble protein, Fv/Fm, Yield, OAA, and K(+)/Na(+)) could be used to evaluate cadmium resistance in Ulva by correlation analysis. In accordance with the order of the absolute values of correlation coefficient, contents of Cd(2+) and K(+), Yield, proline content, Fv/Fm, FAA content, and OAA value of Ulva were more highly related to their adaptation to Cd(2+) than the other eight indices. Thus, U. linza has a better adaptation to Cd(2+) than U. prolifera, which was due mainly to higher nutrient content and stronger OAA and photosynthesis in U. linza.

Poly(dimethyl siloxane) (PDMS) network blends of amphiphilic acrylic copolymers with poly(ethylene glycol)-fluoroalkyl side chains for fouling-release coatings. II. Laboratory assays and field immersion trials.

Amphiphilic copolymers containing different amounts of poly(ethylene glycol)-fluoroalkyl acrylate and polysiloxane methacrylate units were blended with a poly(dimethyl siloxane) (PDMS) matrix in different proportions to investigate the effect of both copolymer composition and loading on the biological performance of the coatings. Laboratory bioassays revealed optimal compositions for the release of sporelings of Ulva linza, and the settlement of cypris larvae of Balanus amphitrite. The best-performing coatings were subjected to field immersion tests. Experimental coatings containing copolymer showed significantly reduced levels of hard fouling compared to the control coatings (PDMS without copolymer), their performance being equivalent to a coating based on Intersleek 700™. XPS analysis showed that only small amounts of fluorine at the coating surface were sufficient for good antifouling/fouling-release properties. AFM analyses of coatings under immersion showed that the presence of a regular surface structure with nanosized domains correlated with biological performance.

Investigation of the role of hydrophilic chain length in amphiphilic perfluoropolyether/poly(ethylene glycol) networks: towards high-performance antifouling coatings.

The facile preparation of amphiphilic network coatings having a hydrophobic dimethacryloxy-functionalized perfluoropolyether (PFPE-DMA; M(w) = 1500 g mol(-1)) crosslinked with hydrophilic monomethacryloxy functionalized poly(ethylene glycol) macromonomers (PEG-MA; M(w) = 300, 475, 1100 g mol(-1)), intended as non-toxic high-performance marine coatings exhibiting antifouling characteristics is demonstrated. The PFPE-DMA was found to be miscible with the PEG-MA. Photo-cured blends of these materials containing 10 wt% of PEG-MA oligomers did not swell significantly in water. PFPE-DMA crosslinked with the highest molecular weight PEG oligomer (ie PEG1100) deterred settlement (attachment) of algal cells and cypris larvae of barnacles compared to a PFPE control coating. Dynamic mechanical analysis of these networks revealed a flexible material. Preferential segregation of the PEG segments at the polymer/air interface resulted in enhanced antifouling performance. The cured amphiphilic PFPE/PEG films showed decreased advancing and receding contact angles with increasing PEG chain length. In particular, the PFPE/PEG1100 network had a much lower advancing contact angle than static contact angle, suggesting that the PEG1100 segments diffuse to the polymer/water interface quickly. The preferential interfacial aggregation of the larger PEG segments enables the coating surface to have a substantially enhanced resistance to settlement of spores of the green seaweed Ulva, cells of the diatom Navicula and cypris larvae of the barnacle Balanus amphitrite as well as low adhesion of sporelings (young plants) of Ulva, adhesion being lower than to a polydimethyl elastomer, Silastic T2.

Physiological and physico-chemical characterization of dietary fibre from the green seaweed Ulva fasciata Delile / Caracterização fisiológica e físico-química da fibra alimentar da macroalga marinha verde Ulva fasciata Delile

This work aims to assess the potential of the green seaweed Ulva fasciata Delile as an alternative source of dietary fibre (DF). Total DF content was determined, some of its physico-chemical properties described and the physiological effects of U. fasciata meal on rats fed a hypercholesterolemic diet were investigated. U. fasciata may be considered a potential alternative source of DF with a total content of about 400 g.kg-1 (dry basis) and interesting physico-chemical properties: water retention capacity of 8.74 g/water.g-1 dry sample (seaweed meal) and 0.90 (seaweed carbohydrate extract), lipid adsorption capacity of 4.52 g/oil.g-1 dry sample (seaweed meal) and 5.70 (seaweed carbohydrate extract), intrinsic viscosity of 2.4 dl.g-1 (seaweed carbohydrate extract) and cation exchange capacity of 3.51 Eq.kg-1 (seaweed carbohydrate extract). The diet containing seaweed meal was able to keep rats' total cholesterol (TC) down without causing any undesirable increase in LDL-C fraction. No evidence of toxic and/or antinutritional components in the seaweed meal was detected. Rats showed a fecal volume much greater (13 g) than that fed on cellulose diet ( 7 g) (p < 0.05). These properties confer on the seaweed the potential to be used in food technology for the acquisition of low-calorie food and might be important in body weight control, reduction of blood TC and LDL-C as well as in prevention of gastrointestinal diseases.

Este trabalho objetivou avaliar o potencial da alga marinha verde Ulva fasciata Delile como fonte alternativa de fibra alimentar. Foram realizadas a determinação do teor de fibra alimentar total e a descrição de algumas propriedades físico-químicas, e os efeitos fisiológicos da farinha da alga seca sobre ratos alimentados com dieta hipercolesterolemizante foram investigados. Esta alga pode ser considerada uma fonte alternativa potencial de fibra com cerca de 400 g.kg-1 (base seca) e propriedades físico-químicas interessantes: uma capacidade de retenção de água de 8,74 g/água.g-1 de amostra seca (farinha de alga) e 0,90 (extrato de carboidratos), uma capacidade de adsorção de lipídeos de 4,52 g/óleo.g-1 de amostra seca (farinha de alga) e 5,70 (extrato de carboidratos), uma viscosidade intrínseca de 2,4 dl.g-1 (extrato de carboidrato da alga) e capacidade de troca iônica de 3,51 Eq.kg-1 (extrato de carboidrato). A dieta contendo farinha de alga foi capaz de manter baixos os níveis de colesterol total de ratos sem causar aumento indesejável na fração LDL-C. Nenhuma evidência de componentes tóxicos e/ou antinutricionais na farinha de alga foi encontrada. Os ratos mostraram um volume fecal maior (13 g) do que aqueles alimentados com dieta contendo celulose como fonte de fibra (7 g) (p < 0,05). Essas propriedades conferem a alga o potencial de ser utilizada na tecnologia de alimentos para a aquisição de alimentos de baixas calorias, podendo ser importante para o controle do peso corporal, redução do colesterol sanguíneo total e da fração LDL-C, como também na prevenção de doenças gastrintestinais.