Host Range and Coding Potential of Eukaryotic Giant Viruses

Giant viruses are a group of eukaryotic double-stranded DNA viruses with large virion and genome size that challenged the traditional view of virus. Newly isolated strains and sequenced genomes in the last two decades have substantially advanced our knowledge of their host diversity, gene functions, and evolutionary history. Giant viruses are now known to infect hosts from all major supergroups in the eukaryotic tree of life, which predominantly comprises microbial organisms. The seven well-recognized viral clades (taxonomic families) have drastically different host range. Mimiviridae and Phycodnaviridae, both with notable intrafamilial genome variation and high abundance in environmental samples, have members that infect the most diverse eukaryotic lineages. Laboratory experiments and comparative genomics have shed light on the unprecedented functional potential of giant viruses, encoding proteins for genetic information flow, energy metabolism, synthesis of biomolecules, membrane transport, and sensing that allow for sophisticated control of intracellular conditions and cell-environment interactions. Evolutionary genomics can illuminate how current and past hosts shape viral gene repertoires, although it becomes more obscure with divergent sequences and deep phylogenies. Continued works to characterize giant viruses from marine and other environments will further contribute to our understanding of their host range, coding potential, and virus-host coevolution.     

Global evaluation of biofuel potential from microalgae

In the current literature, the life cycle, technoeconomic, and resource assessments of microalgae-based biofuel production systems have relied on growth models extrapolated from laboratory-scale data, leading to a large uncertainty in results. This type of simplistic growth modeling overestimates productivity potential and fails to incorporate biological effects, geographical location, or cultivation architecture. This study uses a large-scale, validated, outdoor photobioreactor microalgae growth model based on 21 reactor- and species-specific inputs to model the growth of Nannochloropsis. This model accurately accounts for biological effects such as nutrient uptake, respiration, and temperature and uses hourly historical meteorological data to determine the current global productivity potential. Global maps of the current near-term microalgae lipid and biomass productivity were generated based on the results of annual simulations at 4,388 global locations. Maximum annual average lipid yields between 24 and 27 m³·ha⁻¹·y⁻¹, corresponding to biomass yields of 13 to 15 g·m⁻²·d⁻¹, are possible in Australia, Brazil, Colombia, Egypt, Ethiopia, India, Kenya, and Saudi Arabia. The microalgae lipid productivity results of this study were integrated with geography-specific fuel consumption and land availability data to perform a scalability assessment. Results highlight the promising potential of microalgae-based biofuels compared with traditional terrestrial feedstocks. When water, nutrients, and CO₂ are not limiting, many regions can potentially meet significant fractions of their transportation fuel requirements through microalgae production, without land resource restriction. Discussion focuses on sensitivity of monthly variability in lipid production compared with annual average yields, effects of temperature on productivity, and a comparison of results with previous published modeling assumptions.Recent volatility in oil prices, attributed to increased demand and limited resources, has led to the development of unconventional petroleum reserves, such as oil sands, and increased exploration of alternative and renewable fuel sources. Scalability limitations associated with traditional terrestrial biofuel feedstocks have renewed interest in next-generation feedstocks, such as microalgae. Microalgae offer many potential advantages over traditional terrestrial oil crops, including higher lipid productivities, a lack of competition for arable land, year-round cultivation, integration with saline and low-quality water sources, and a viable drop-in equivalent fuel product (1–5). These scalable advantages make microalgae a promising feedstock for biofuel production and a potential sustainable alternative to traditional petroleum fuels.The current near-term productivity potential for microalgae at large-scale currently is being estimated through the linear scaling of laboratory-based growth and lipid data, which has led to a large variance in reported values (4, 6). This type of scaling has been integrated into various life cycle, technoeconomic, and resource models of the microalgae-to-biofuels process, leading to unrealistic assumptions about industrial function, and is a source of large uncertainty (2). Current near-term algal lipid productivity values reported in life cycle, technoeconomic, and resource modeling literature range from 2.3 m³·ha⁻¹·y⁻¹ reported by Ramachandra et al. (6) to 136.9 m³·ha⁻¹·y⁻¹ reported by Mata et al. (4), with a variety of researchers reporting values between these two extremes (1, 3–26). Large uncertainty in the reported productivity potentials stems from the use of simplistic growth modeling through simple solar conversion calculations or linear scaling of laboratory data; both fail to incorporate biological function and geographic diversity. Propagation of errors in microalgae production modeling at large-scale skew life cycle, economic, and scalability assessments, because lipid yield typically represents the functional unit in these assessments.Decreasing uncertainty in the current productivity potential from microalgae requires increased fidelity in growth modeling through temporal and biological resolution combined with geographically specific climatic and resource data (27). This study integrates a microalgae growth model with hourly historical meteorological data from various global locations for the assessment of the current near-term lipid and biomass productivity potential of microalgae cultivated in a traditional closed-system photobioreactor. The microalgae growth and lipid content is simulated on an hourly time scale over the course of 1 y at 4,388 global locations through the use of 12–25 y (depending on site) of meteorological data. Results from annual simulations were surface interpolated to produce a dynamic global map of the current near-term microalgae lipid productivity and are intended to represent the current large-scale production potential based on a photobioreactor architecture. Discussion focuses on the effects of temperature on productivity, a geographically specific scalability assessment, monthly variability in productivity, and a comparison of modeled results with current near-term productivity potentials reported in microalgae biofuel life cycle, technoeconomic, and scalability literature.     

Cell death and inhibition of population growth of marine unicellular algae by pesticides

The marine diatom, Skeletonema costatum, was exposed to the pesticides hexachlorocyclopentadiene, EPN, chlorpyrifos, carbophenothion, and Atrazine and examined for death of cells with Evans blue, a mortal stain. All pesticides caused death of cells, but significant mortality occurred only at concentrations greater than the EC₅₀ calculated from population growth studies. The insecticide, Amdro^®, did not kill the marine algae S. costatum, Thalassiosira pseudonana, Isochrysis galbana, Chlorella sp., or Dunaliella tertiolecta. However, Amdro was very inhibitory to algal population growth at low concentrations, i.e. EC₅₀ values at 48 h were between 0.14 ppb for T. pseudonana and 10.3 ppb for D. tertiolecta. EC₅₀ values were lowest after 48 h of exposure in tests conducted for 96 h. By 96 h after exposure, maximum growth rates of treated cultures were approximately those of control cultures. It is recommended that, because of problems associated with the fate of toxicants, algal laboratory toxicity tests be conducted for 48 to 72 h instead of the usual 96 h or longer.     

褐藻多糖抗病毒作用研究进展

近年来,针对海洋多糖抗病毒作用的研究越来越受到人们的重视,特别是海藻多糖在开发抗病毒药物方面具有极大的潜力。本文将就褐藻多糖特别是类肝素的褐藻硫酸多糖在抗病毒作用方面的研究进展作一综述,系统地总结褐藻多糖的分类及结构特征,抗病毒活性及其作用机制,以期为褐藻多糖的开发利用及抗病毒多糖药物的研发提供借鉴和参考。     

Antitrypanosomal in vitro activity of tropical marine algae extracts

Trypanosomiasis is one of the most important parasitic diseases worldwide. The undesirable side effects and low efficacy of classical trypanocidal drugs underline the necessity of the development of new drugs from natural products. Although marine algae have been recognized as attractive sources of known and novel bioactive compounds, very little research has been focused on antiprotozoal activity. Aqueous and organic extracts of 29 species of marine algae (14 species of Rhodophyta, seven species of Phaeophyta, and eight species of Chlorophyta) collected from the Gulf of Mexico and Caribbean coast of the Yucatan Peninsula (Mexico) were evaluated for their antiprotozoal activity in vitro against Trypanosoma cruzi trypomastigotes. The toxicity of these extracts was evaluated using brine shrimp (Artemia salina). The cytotoxicity on mammalian cells was also assessed by the MTT viability assay. The organic extracts from Dictyota caribea Horning & Schnetter, Lobophora variegata (J.V. Lamouroux) Womersley, Turbinaria turbinata Linnaeus, and Laurencia microcladia Kützing possess promising in vitro activity against T. cruzi trypomastigotes. The toxicity displayed by Laurencia microcladia against Artemia salina and the high cytotoxicity exhibited by T. turbinata must be taken into account in further studies.     

Broad-scale predictability of carbohydrates and exopolymers in Antarctic and Arctic sea ice

Sea ice can contain high concentrations of dissolved organic carbon (DOC), much of which is carbohydrate-rich extracellular polymeric substances (EPS) produced by microalgae and bacteria inhabiting the ice. Here we report the concentrations of dissolved carbohydrates (dCHO) and dissolved EPS (dEPS) in relation to algal standing stock [estimated by chlorophyll (Chl) a concentrations] in sea ice from six locations in the Southern and Arctic Oceans. Concentrations varied substantially within and between sampling sites, reflecting local ice conditions and biological content. However, combining all data revealed robust statistical relationships between dCHO concentrations and the concentrations of different dEPS fractions, Chl a, and DOC. These relationships were true for whole ice cores, bottom ice (biomass rich) sections, and colder surface ice. The distribution of dEPS was strongly correlated to algal biomass, with the highest concentrations of both dEPS and non-EPS carbohydrates in the bottom horizons of the ice. Complex EPS was more prevalent in colder surface sea ice horizons. Predictive models (validated against independent data) were derived to enable the estimation of dCHO concentrations from data on ice thickness, salinity, and vertical position in core. When Chl a data were included a higher level of prediction was obtained. The consistent patterns reflected in these relationships provide a strong basis for including estimates of regional and seasonal carbohydrate and dEPS carbon budgets in coupled physical-biogeochemical models, across different types of sea ice from both polar regions.Sea ice covers extensive regions of the Arctic and Southern Oceans, as well as some subpolar seas, and exhibits major annual, interannual, and long-term climate-related variability in age, thickness, and structure (1–3). Sea ice is not an inert physical barrier to air–ocean exchange (4), and both microbial activity and physico-chemical reactions within the ice contribute to regional-scale biogeochemical processes at the air–ocean surface interface (5).Sea ice provides a range of habitats for diverse biological assemblages that are characterized by high standing stocks of microalgae and bacteria (6). These microorganisms produce large quantities of dissolved organic carbon (DOC), often in the form of carbohydrate-rich extracellular polymeric substances (EPS) (7). Microbial EPS exist in a dynamic equilibrium from dissolved polysaccharides (dEPS <0.2 µm) to complex particulate EPS that can form gels on the millimeter to centimeter scale (8). Here we focus on the biologically relevant dissolved carbohydrates (dCHO) that constitute a substantial fraction of the DOC in sea ice (9–13) (Fig. 1). dCHO are concentrated from sea ice DOC by dialysis (>8 kDa), with subsequent treatment allowing the definition of four subcomponents of the total dCHO pool: (i) dissolved uronic acids (dUA), produced by ice diatoms and ice bacteria (14–16), that confer strong cross-linkages between polymer chains (8), forming low solubility EPS complexes within brine channels (8, 14, 17); (ii) dEPS, produced by sea ice algae (9, 12, 18, 19) and isolated from dCHO by 70% (vol/vol) alcohol precipitation; (iii) a low solubility fraction of dEPS obtained by 30% (vol/vol) alcohol precipitation, containing complex EPS molecules (dEPS_complex), often produced by algae with reduced biological activity or when under physiological stress (9, 13, 19); and (iv) a fraction of highly soluble carbohydrates that are not considered EPS (dCHO_non-EPS), do not precipitate in alcohol, and are produced by many actively growing ice algae (9, 14).Open in a separate windowFig. 1.Representation of the molecular-size spectrum from large polysaccharides to low molecular-weight components of the total DOC pool (<0.2 µm) in melted sea ice, and partitioning of DOC into dCHO, dUA (by dialysis >8 kDa), dEPS, complex dEPS, and non-EPS carbohydrate fractions (by alcohol precipitation). Dotted boxes indicate a subcomponent of the main category.The bacteria and algae that successfully colonize sea ice habitats have mechanisms that enable them to survive temperatures less than −20 °C and salinities >100 in the sea ice brines (17, 20). However, there is increasing evidence that the processes of seawater freezing can be biologically mediated by ice-binding proteins and EPS secreted by bacteria and algae. These compounds can alter ice structure (14, 15, 21–26) and, in the case of EPS, also form physico-chemical buffers between the organisms and the surrounding brines and ice matrix (9, 14, 17).When sea ice melts, its dissolved and particulate constituents are released into the surface waters (27, 28), contributing to the microbial dynamics in both the melting ice and melt waters (19, 29–31). Physical aggregation of EPS in seawater to form larger particles may promote the sinking of particulate organic matter from the surface waters (19, 32), or produce EPS foams that are a source of aerosol particles, which are thought to have an active role in atmospheric nucleation processes in the Arctic (33).The growing evidence of the important role played by microbial EPS in sea ice, coupled with the changes in the extent and duration of ice cover in the polar seas (3), makes obtaining a quantitative understanding of EPS in sea ice important. Here we present a synthesis of data on dCHO—and its constituents—from sea ice samples from the Arctic and Southern Oceans, covering different seasons and variable microbial standing stocks. Our aim was to identify trends in the relationships between components of dEPS and fundamental parameters, such as temperature, ice thickness, and algal standing stock in sea ice. Using this dataset we present predictive models that can allow the estimation of dCHO and dEPS in sea ice and the potential mass of these carbon-rich organic substances on regional scales.     

Anti-Cancer Mechanism and Possibility of Nano-Suspension Formulation for a Marine Algae Product Fucoxanthin

Recently, use of natural products available from marine sources, and especially algae products, are receiving more attention. Scientific evidence for claimed nutraceutical and therapeutical effects of one such marine algae product, fucoxanthin, is discussed in this paper with a summary of the currently available literature regarding its antioxidant, anti-obesity and anticancer activities. It is safe for use in humans, but as it has poor solubility a nano-suspension mode of delivery may be adopted to improve efficacy of supplments. We conclude from ourliterature review that the marine algae product fucoxanthin has significant antioxidant, anti-obesity and anticancer activity with established mechanisms of action.     

Cytotoxic and protective DNA damage of three new diterpenoids from the brown alga Dictoyota dichotoma

Three new diterpenes Amijiol acetate (3), dolabellane, Dolabellatrienol (4), and dolastane, Amijiol-7, 10-diacetate (9) were isolated together with the previously described Pachydictyol A (1), Isopachydictyol A (2), 8β-hydroxypachydictyol A (5), Amijiol (6), Isodictyohemiacetal (7) and Dictyol C (8) from the Red Sea brown alga Dictyota dichotoma var. implexa. The structures and relative stereochemistry of the new diterpenoids were proposed on the basis of their spectral data. Compounds 3 and 9 have potent activity against DNA damage, cytotoxicity against WI-38, HepG2, and MCF-7 cell lines, and antioxidant using ABTS and erythrocytes hemolysis.     

In vitro and in vivo safety assessment of edible blue-green algae, Nostoc commune var. sphaeroides Kützing and Spirulina plantensis

Blue-green algae (BGA) have been consumed as food and herbal medicine for centuries. However, safety for their consumption has not been well investigated. This study was undertaken to evaluate in vitro and in vivo toxicity of cultivated Nostoc commune var. sphaeroides Kützing (NO) and Spirulina platensis (SP). Neither NO nor SP contained detectable levels of microcystin (MC)-LA, MC-RR, MC-LW and MC-LR by LC/MS/MS. Cell viability remained ∼70-80% when HepG2 cells were incubated with 0-500 μg/ml of hexane, chloroform, methanol and water-extractable fractions of NO and SP. Four-week-old male and female C57BL/6J mice were fed an AIN-93G/M diet supplemented with 0%, 2.5% or 5% of NO and SP (wt/wt) for 6 months. For both genders, BGA-rich diets did not induce noticeable abnormality in weight gain and plasma alanine aminotransferase (ALT) and aspartate aminotransferase concentrations except a significant increase in plasma ALT levels by 2.5% NO supplementation in male mice at 6 month. Histopathological analysis of livers, however, indicated that BGA did not cause significant liver damage compared with controls. In conclusion, our results suggest that NO and SP are free of MC and the long-term dietary supplementation of up to 5% of the BGA may be consumed without evident toxic side-effects.     

Phytochelatin formation kinetics and toxic effects in the freshwater alga Chlamydomonas reinhardtii upon short- and long-term exposure to lead(II)

Phytochelatins (PC) are metal-binding ligands synthesized by algae in response to elevated concentrations of various metals, such as Pb. Kinetics of PC synthesis and Pb accumulation in Chlamydomonas reinhardtii were investigated as a function of [Pb²⁺] = 10⁻¹¹-10⁻⁷ M (pPb11-pPb7.1) in the exposure medium for up to 6 h. The role of PC in Pb detoxification was explored by relating PC synthesis to the effects of Pb on growth and photosynthetic yield upon exposure to pPb9 and pPb8.3 for up to 72 h. Pb accumulation increased with increasing [Pb²⁺], reaching a maximum concentration of 596 ± 77 amol/cell (intracellular concentration 2.98 mM) at pPb7.1. Low concentrations of PC₂-PC₄ were present in C. reinhardtii grown in control media without Pb addition. Upon short-term exposure, PC₂ and PC₃ synthesis was induced within minutes at [Pb²⁺] ≥ pPb8 and PC₄ synthesis after a lag phase at pPb7.1. Cellular PC₂-PC₄ concentrations increased with time over 6 h and with increasing [Pb²⁺]. PC concentrations after 6 h exposure to pPb7.1 were 28.5 ± 0.2 amol/cell (142 μM) PC₂, 2.8 ± 0.05 amol/cell (14 μM) PC₃ and 0.30 ± 0.01 amol/cell (1.5 μM) PC₄. Upon long-term exposure, induction of PC synthesis was detected at pPb9 and synthesis of PCs with a higher degree of polymerization was observed (PC₅). PC concentrations were lower than intracellular Pb and were thus not present at sufficiently high concentrations to immobilize accumulated Pb. Inhibition of photosynthesis and growth up to 100% was observed upon long-term exposure, whereas in short-term experiments no inhibitory effects were detected.