Green Alga Dunaliella Tertiolecta Research Articles

Effect of heavy metals on protein content of marine unicellular green alga Dunaliella tertiolecta.

Microalgae are rich source of protein containing necessary amino acids at different levels. The present study was designed to assess stimulatory and/or inhibitory impact of five different concentrations (5, 10, 15, 20, and 25mg/L) of three essential heavy metals (nickel, zinc, and copper) on protein content (soluble, insoluble, and total) of the marine unicellular green alga Dunaliella tertiolecta. Further, geospatial analyses were used to assess the suitability of Qaroun Lake for D. tertiolecta proliferation. The experimental results showed a gradual increase in protein content of D. tertiolecta with low concentrations of the three investigated heavy metals. However, increasing levels of heavy metals led to inhibitory effect on protein synthesis in alga with different grades. Ni, Zn and Cu levels in Qaroun lake were found suitable for the proliferation of Dunaliella (Lower than 5mg/L). The present study highly recommends the necessity to encourage site selection of optimal marine environments suitable for the proliferation of marine algae rich in protein content.

Fatty Acid Production and Direct Acyl Transfer through Polar Lipids Control TAG Biosynthesis during Nitrogen Deprivation in the Halotolerant Alga Dunaliella tertiolecta.

The aims of this work were to evaluate the contribution of the free fatty acid (FA) pool to triacylglyceride (TAG) biosynthesis and to try to characterize the mechanism by which FA are assimilated into TAG in the green alga Dunaliella tertiolecta. A time-resolved lipidomic analysis showed that nitrogen (N) deprivation induces a redistribution of total lipidome, particularly of free FA and major polar lipid (PL), in parallel to enhanced accumulation of polyunsaturated TAG. The steady-state concentration of the FA pool, measured by prolonged 14C-bicarbonate pre-labeling, showed that N deprivation induced a 50% decrease in total FA level within the first 24 h and up to 85% after 96 h. The abundance of oleic acid increased from 50 to 70% of total free FA while polyunsaturated FA (PUFA) disappeared under N deprivation. The FA flux, measured by the rate of incorporation of 14C-palmitic acid (PlA), suggests partial suppression of phosphatidylcholine (PC) acyl editing and an enhanced turnover of the FA pool and of total digalactosyl-diacylglycerol (DGDG) during N deprivation. Taken together, these results imply that FA biosynthesis is a major rate-controlling stage in TAG biosynthesis in D. tertiolecta and that acyl transfer through PL such as PC and DGDG is the major FA assimilation pathway into TAG in that alga and possibly in other green microalgae. Increasing the availability of FA could lead to enhanced TAG biosynthesis and to improved production of high-value products from microalgae.

Mass transfer and flow characterization of novel algae-based nutrient removal system

BackgroundRecirculating aquaculture systems (RAS) are an essential component of sustainable inland seafood production. Still, nutrient removal from these systems can result in substantial environmental problems, or present a major cost factor with few added value options. In this study, an innovative and energy-efficient algae based nutrient removal system (NRS) was developed that has the potential to generate revenue through algal commercialization. We optimized mass transfer in our NRS design using novel aeration and mixing technology, using air lift pumps and developed an original membrane cartridge for the continuous operation of nutrient removal and algae production. Specifically, we designed, manufactured and tested a 60-L NRS prototype. Based on specific airlift mixing conditions as well as concentration gradients, we assessed NRS nutrient removal capacity. We then examined the effects of different internal bioreactor geometries and radial orientations on the mixing efficiency.ResultsUsing the start-up dynamic method, the overall mass transfer coefficient was found to be in the range of 0.00164–0.0074 {mathrm{s}}^{-1}, depending on flow parameters and we confirmed a scaling relationship of mass transfer across concentration gradients. We found the optimal Reynolds number to be 500 for optimal mass transfer, as higher Reynolds numbers resulted in a relatively reduced increase of mass transfer. This relationship between mass transfer and Reynolds number is critical to assess scalability of our system. Our results demonstrate an even distribution of dissolved oxygen levels across the reactor core, demonstrating adequate mixing by the airlift pump, a critical consideration for optimal algal growth. Distribution of dissolved gases in the reactor was further assessed using flow visualization in order to relate the bubble distribution to the mass transfer capabilities of the reactor. We run a successful proof of principle trial using the green alga Dunaliella tertiolecta to assess mass transfer of nutrients across the membrane and biomass production.ConclusionsManipulation of the concentration gradient across the membrane demonstrates a more prominent role of airlift mixing at higher concentration gradients. Specifically, the mass transfer rate increased threefold when the concentration gradient was increased 2.5-fold. We found that we can grow algae in the reactor chamber at rates comparable to those of other production systems and that the membrane scaffolds effectively remove nutrients form the wastewater. Our findings provide support for scalability of the design and support the use of this novel NRS for nutrient removal in aquaculture and potentially other applications.

Cell size influences inorganic carbon acquisition in artificially selected phytoplankton.

Cell size influences the rate at which phytoplankton assimilate dissolved inorganic carbon (DIC), but it is unclear whether volume-specific carbon uptake should be greater in smaller or larger cells. On the one hand, Fick's Law predicts smaller cells to have a superior diffusive CO2 supply. On the other, larger cells may have greater scope to invest metabolic energy to upregulate active transport per unit area through CO2 -concentrating mechanisms (CCMs). Previous studies have focused on among-species comparisons, which complicates disentangling the role of cell size from other covarying traits. In this study, we investigated the DIC assimilation of the green alga Dunaliella tertiolecta after using artificial selection to evolve a 9.3-fold difference in cell volume. We compared CO2 affinity, external carbonic anhydrase (CAext ), isotopic signatures (δ13 C) and growth among size-selected lineages. Evolving cells to larger sizes led to an upregulation of CCMs that improved the DIC uptake of this species, with higher CO2 affinity, higher CAext and higher δ13 C. Larger cells also achieved faster growth and higher maximum biovolume densities. We showed that evolutionary shifts in cell size can alter the efficiency of DIC uptake systems to influence the fitness of a phytoplankton species.

Type II-Metacaspases are involved in cell stress but not in cell death in the unicellular green alga Dunaliella tertiolecta.

Ultraviolet radiation (UVR; 280–400 nm) has a great impact on aquatic ecosystems by affecting ecophysiological and biogeochemical processes as a consequence of the global change scenario generated by anthropogenic activities. We studied the effect of PAR (P)+UVA (A)+UVB (B) i.e. PAB, on the molecular physiology of the unicellular green alga Dunaliella tertiolecta for six days. We assessed the relationship between the triggered UVR stress response and metacaspases and caspase-like (CL)activities, which are proteases denoted to participate in cell death (CD) in phytoplankton. UVR inhibited cell growth and in vivo chlorophyll a fluorescence but did not cause cell death. Western blot analyses reflected that Type-II metacaspases (MCs) are present and appear to be involved in UVR induced-cell stress but not in dark-induced CD in D. tertiolecta. Enzyme kinetics revealed that cleavage of the MCs-reporter substrates RVRR, QRR, GRR, LKR, HEK, and VLK was 10-fold higher than WEHD, DEVD, IETD, and LETD CLs-substrates. The lowest apparent Michaelis-Menten constants (KMap) corresponded to RVRRase (37.5 μM) indicating a high affinity by the RVRR substrate. The inhibition of enzymatic activities by using inhibitors with different target sites for hydrolyses demonstrated that from all of the R/ Kase activities only RVRRase was a potential candidate for being a metacaspase. In parallel, zymograms and peptide-mass fingerprinting analyses revealed the identities of such Rase activities suggesting an indirect evidence of possible natural physiological substrates of MCs. We present evidence of type II-MCs not being involved in CD in D. tertiolecta, but rather in survival strategies under the stressful irradiance conditions applied in this study.

Isolation and genome analysis of Winogradskyella algicola sp. nov., the dominant bacterial species associated with the green alga Dunaliella tertiolecta

Microalgae and bacteria are known to be closely associated in diverse environments. To isolate dominant bacterial species associated with a green alga, Dunaliella tertiolecta, a photoreactor culture of the microalga was investigated using culture-based and culture-independent approaches. The bacterial community structure of the algal culture showed that the most abundant bacterial species under the culture conditions was related to the genus Winogradskyella. The closely related amplicon sequences, showing ≥ 99.5% 16S rRNA gene sequence similarity to one of the isolates, designated IMCC-33238T, constituted > 49% of the bacterial community and was therefore regarded as the most dominant species in the algal culture. Strain IMCC33238T was characterized by Gramstaining-negative and orange-colored rods. Phylogenetic analyses of the 16S rRNA genes as well as whole genome sequences revealed that strain IMCC33238T belonged to Winogradskyella and shared more than 97.2% 16S rRNA gene sequence similarity with Winogradskyella species. The strain contained iso-C15:1 G, iso-C15:0, iso-C15:0 3-OH, and summed feature 3 (C16:1ω6c and/or C16:1ω7c) as major fatty acids and MK-6 as the predominant quinone. The polar lipids found in strain IMCC33238T were phosphatidylethanolamine, two unidentified aminolipids, and three unidentified lipids. The genome of strain IMCC33238T was 3.37 Mbp in size with 33.9 mol% G + C content and proteorhodopsin. Many genes encoding folate and vitamin production are considered to play an important role in the bacteria-algae interaction. On the basis of phylogenetic and phenotypic characteristics, strain IMCC33238T represents a novel species in the genus Winogradskyella, for which the name Winogradskyella algicola sp. nov. is proposed. The type strain is IMCC33238T (= KACC 21192T = NBRC 113704T).

The ratio of single-turnover to multiple-turnover fluorescence varies predictably with growth rate and cellular chlorophyll in the green alga Dunaliella tertiolecta.

Marine phytoplankton experience a wide range of nutrient and light conditions in nature and respond to these conditions through changes in growth rate, chlorophyll concentration, and other physiological properties. Chlorophyll fluorescence is a non-invasive and efficient tool for characterizing changes in these physiological properties. In particular, the introduction of fast repetition rate fluorometry (FRRf) into studies of phytoplankton physiology has enabled detailed studies of photosynthetic components and kinetics. One property retrieved with an FRRf is the 'single-turnover' maximum fluorescence (FmST) when the primary electron acceptor, Qa, is reduced but the plastoquinone (PQ) pool is oxidized. A second retrieved property is the 'multiple-turnover' fluorescence (FMT) when both Qa and PQ are reduced. Here, variations in FmST and FMT were measured in the green alga Dunaliella tertiolecta grown under nitrate-limited, light-limited, and replete conditions. The ratio of FmST to FMT (ST/MT) showed a consistent relationship with cellular chlorophyll in D. tertiolecta across all growth conditions. However, the ST/MT ratio decreased with growth rate under nitrate-limited conditions but increased with growth rate under light-limited conditions. In addition, cells from light-limited conditions showed a high accumulation of Qb-nonreducing centers, while cells from nitrate-limited conditions showed little to none. We propose that these findings reflect differences in the reduction and oxidation rates of plastoquinone due to the unique impacts of light and nitrate limitation on the stoichiometry of light-harvesting components and downstream electron acceptors.

TiO2 nanoparticles in seawater: Aggregation and interactions with the green alga Dunaliella tertiolecta

Titanium dioxide nanoparticles (TiO2 NPs) have been widely employed in industrial applications, thus rising concern about their impact in the aquatic environment. In this study we investigated the chemical behaviour of TiO2 NPs in the culture medium and its effect on the green alga Dunaliella tertiolecta, in terms of growth inhibition, oxidative stress, ROS (Reactive Oxygen Species) accumulation and chlorophyll content. In addition, the influence of exopolymeric substances (EPS) excreted by the microalgae on the stability of NPs has been evaluated. The physicochemical characterization showed a high propensity of TiO2 NPs to form micrometric-sized aggregates within 30min, large enough to partially settle to the bottom of the test vessel. Indeed, an increasing amount of TiO2 particles settled out with time, but the presence of EPS seemed to mitigate this behaviour in the first 6h of exposure where the main effects in D. tertiolecta were observed. TiO2 NPs did not inhibit the 72-h growth rate of D. tertiolecta, nor affected the cellular chlorophyll concentration in the range 0.01–10mgL−1. The time-course of ROS production showed an initial transient increase of ROS in TiO2 NP-exposed algae compared to the control, concomitant with an enhancement of catalase activity. Interestingly, intracellular ROS was a small fraction of total ROS, the highest amount being extracellular. The occurrence of cell-mediated chemical transformations of TiO2 NPs in the external medium, related to the presence of EPS, has been evaluated. Our results showed that carbohydrates were the major component of EPS, whereas proteins of medium molecular weight (20–80kDa) were preferentially bound to TiO2 NPs, likely influencing their biological fate.

Don't just dump your data and run: Authors should submit as much experimental information as possible when uploading sequence data.

If you have, in any way, been involved with genetic research over the past 10 years, then you have likely heard of the Sequence Read Archive (SRA), which is jointly housed at the National Center for Biotechnology (NCBI), the DNA Data Bank of Japan (DDBJ), and the European Bioinformatics Institute (EBI). And if you regularly work with genome or transcriptome sequence information, then you have probably extracted data from and/or deposited data into the SRA. For those who are unfamiliar with it, the SRA is an international public online archive for next‐generation sequencing (NGS) data, which was established about a decade ago under the guidance of the International Nucleotide Sequence Database Collaboration (INSDC) [1], [2]. Despite nearly being shut down in 2011 [3], it has grown at a staggering rate over the past 10 years. As of September 1, 2017, it housed over five quadrillion (1015) open‐access bases of NGS data, coming from thousands of different species and spanning the entire gamut of cellular and viral life. It contains DNA‐ and RNA‐sequencing (DNA‐seq and RNA‐seq) reads of every kind, from bisulfite‐seq to strand‐specific RNA‐seq to single‐cell DNA‐seq, and it accepts reads from every type of NGS platform, be it Illumina, Ion Torrent, or PacBio sequencing. In other words, the SRA is a crucial and central resource in the fast‐paced and increasingly important domain of contemporary genetic research. > … the SRA is a crucial and central resource in the fast‐paced and increasingly important domain of contemporary genetic research. ### The Sequence Read Archive The SRA can be easily accessed and searched via the NCBI (https://www.ncbi.nlm.nih.gov/sra), DDBJ (http://trace.ddbj.nig.ac.jp/dra/index_e.html), and EBI (http://www.ebi.ac.uk/ena/submit/read-submission) websites. Once there, you will find yourself at a sequencing‐read superstore. With a decent Wi‐Fi connection, a couple of keyword searches, and a few clicks of the trackpad, you can quickly …

Triacylglycerol is produced from starch and polar lipids in the green alga Dunaliella tertiolecta.

The halotolerant green alga Dunaliella tertiolecta accumulates starch and triacylglycerol (TAG) amounting to 70% and 10-15% of total cellular carbon, respectively, when exposed to nitrogen (N) deprivation. The purpose of this study was to clarify the inter-relationships between the biosynthesis of TAG, starch, and polar lipids (PLs) in this alga. Pulse labeling with [14C]bicarbonate was utilized to label starch and [14C]palmitic acid (PlA) to label lipids. Transfer of 14C into TAG was measured and used to calculate rates of synthesis. About two-thirds of the carbon in TAG originates from starch, and one-third is made de novo by direct CO2 assimilation. The level made from degradation of pre-formed PLs is estimated to be very small. Most of the de novo synthesis involves fatty acid transfer through PLs made during the first day of N deprivation. The results suggest that starch made by photosynthetic carbon assimilation at the early stages of N deprivation is utilized for synthesis of TAG. Trans-acylation from PLs is the second major contributor to TAG biosynthesis. The utilization of starch for TAG biosynthesis may have biotechnological applications to optimize TAG biosynthesis in algae.

A 2-O-Methylriboside Unknown Outside the RNA World Contains Arsenic.

Lipid-soluble arsenic compounds, also called arsenolipids, are ubiquitous marine natural products of currently unknown origin and function. In our search for clues about the possible biological roles of these compounds, we investigated arsenic metabolism in the unicellular green alga Dunaliella tertiolecta, and discovered an arsenolipid fundamentally different from all those previously identified; namely, a phytyl 5-dimethylarsinoyl-2-O-methyl-ribofuranoside. The discovery is of particular interest because 2-O-methylribosides have, until now, only been found in RNA. We briefly discuss the significance of the new lipid in biosynthesis and arsenic biogeochemical cycling.

The effect of wetting property on anti-fouling/foul-release performance under quasi-static/hydrodynamic conditions

In this study, we synthesized hydrophilic and hydrophobic polyacrylate resin using free-radical polymerization and embedded cupric ion source (Cu2O) into the as-prepared resins to fabricate antifouling coatings, such of that the coatings combine the concept of “antifouling” and “fouling release” properties. In particular, the effect of hydrophobicity/hydrophilicity on anti-biofouling was investigated. The physicochemical properties of the coatings were characterized by infrared spectroscopy, atomic absorption spectroscopy, and contact angle measurements. Biofouling assays for the settlement and release of the diatom Navicula sp. and green alga Dunaliella tertiolecta were carried out under quasi-static and hydrodynamic condition. To prove the chemical stability and broad-spectrum antifouling characteristics of these coatings, the field tests were implemented in the South China Sea. Both results show that hydrophilic coating exhibits superior foul-resistance behavior to the hydrophobic coatings probably because of larger cupric ion release rate and the inhibition of hydrophobic interaction on hydrophilic coating.

Toxicological effects of CdSe/ZnS quantum dots on marine planktonic organisms

Quantum dot nanoparticles (QDs) are proposed as novel materials for photovoltaic technologies, light emitting devices, and biomedical applications. In this study we investigated the effect of CdSe/ZnS QDs on the growth rate of four microalgae: the diatom Phaeodactylum tricornutum, the cryptophyte Rhinomonas reticulata, the prymnesiophyte Isochrysis galbana and the green alga Dunaliella tertiolecta. In addition we analyzed the effect of QDs on the copepod Acartia tonsa. A classical acute test (48-h) with embryos was carried out to evaluate naupliar survival. Moreover, a 4-day chronic test with adult copepods was conducted to evaluate their fecundity (embryos f−1day−1) and egg hatching success. QDs in the range from 1 to 4nM gradually inhibited the growth rate of P. tricornutum, I. galbana, R. reticulata and D. tertiolecta with an EC50 of 1.5, 2.4, 2.5 and 4.2nM, respectively. Acute tests with A. tonsa (QD concentration tested from 0.15 to 1.5nM) showed an increased naupliar mortality in response to QD treatment, exhibiting an EC50 of 0.7nM. Chronic test showed no negative effect on egg production, except on the last two days at the highest QD concentration (2.5nM). No significant reduction of the percentage of egg hatching success was recorded during the exposure. Toxicity assessment of QDs was also investigated at the molecular level, studying heat shock protein 70 gene expression (hsp 70). Our results indicate that hsp70 was upregulated in adults exposed 3 days to 0.5nM QDs. Overall, these results suggest that species unable to swim along the water column, like P. tricornutum and early hatched copepods, could be more exposed to toxic effects of QDs which tend to aggregate and settle in seawater.

Physiological response of the green microalgae Dunaliella tertiolecta against imidazolium ionic liquids [bmim][BF4] and/or [omim][BF4]: the role of salinity on the observed effects

The ability of two widely used imidazolium-based ionic liquids (ILs) to affect the physiological behavior of the green alga Dunaliella tertiolecta treated in culture media with different salinities (30 and 35 ‰) was investigated. Algae species were exposed to 1-butyl-3-methylimidazolium tetrafluoroborate ([bmim][BF4]), 1-octyl-3-methylimidazolium tetrafluoroborate ([omim][BF4]), and their binary mixture [bmim][BF4]–[omim][BF4] (ratio 1:1) for 96 h, in f/2 medium with different salinities (30 and 35 ‰). Every 24 h, the growth rate (μ) and the percent inhibition (% I) as well as the concentrations of carotenoids (in terms of carotene content) and chlorophyll a (Chl a) were determined. According to the results, the culture media salinity plays a key role in IL-mediated inhibitory effects on algae. In both salinities, ILs can act against algal growth rate rather than Chl a synthesis, merely due to the existence of a cross-linking with carotenoids, whose enhancement prior or in parallel with Chl a synthesis could play an important role against their growth restriction.

Derivation of a water quality guideline for aluminium in marine waters

Metal risk assessment of industrialized harbors and coastal marine waters requires the application of robust water quality guidelines to determine the likelihood of biological impacts. Currently there is no such guideline available for aluminium in marine waters. A water quality guideline of 24 µg total Al/L has been developed for aluminium in marine waters based on chronic 10% inhibition or effect concentrations (IC10 or EC10) and no-observed-effect concentrations (NOECs) from 11 species (2 literature values and 9 species tested including temperate and tropical species) representing 6 taxonomic groups. The 3 most sensitive species tested were a diatom Ceratoneis closterium (formerly Nitzschia closterium; IC10 = 18 µg Al/L, 72-h growth rate inhibition) < mussel Mytilus edulis plannulatus (EC10 = 250 µg Al/L, 72-h embryo development) < oyster Saccostrea echinata (EC10 = 410 µg Al/L, 48-h embryo development). Toxicity to these species was the result of the dissolved aluminium forms of aluminate (Al(OH4 (-) ) and aluminium hydroxide (Al(OH)3 (0) ) although both dissolved, and particulate aluminium contributed to toxicity in the diatom Minutocellus polymorphus and green alga Dunaliella tertiolecta. In contrast, aluminium toxicity to the green flagellate alga Tetraselmis sp. was the result of particulate aluminium only. Four species, a brown macroalga (Hormosira banksii), sea urchin embryo (Heliocidaris tuberculata), and 2 juvenile fish species (Lates calcarifer and Acanthochromis polyacanthus), were not adversely affected at the highest test concentration used.

EFFECTS OF DIFFERENT POTENTIAL FOOD SOURCES ON UPPER-BATHYAL BENTHIC FORAMINIFERA: AN EXPERIMENT WITH PROPAGULES

Research Article| October 01, 2014 EFFECTS OF DIFFERENT POTENTIAL FOOD SOURCES ON UPPER-BATHYAL BENTHIC FORAMINIFERA: AN EXPERIMENT WITH PROPAGULES Christopher J. Duffield; Christopher J. Duffield 4 1Department of Geosciences, University of Oslo, P.O. Box 1047 Blindern, 0316 Oslo, Norway 4Correspondence author. E-mail: c.j.duffield@geo.uio.no Search for other works by this author on: GSW Google Scholar Bente Edvardsen; Bente Edvardsen 2Department of Biosciences, University of Oslo, P.O. Box 1066, Blindern, N-0316 Oslo, Norway Search for other works by this author on: GSW Google Scholar Wenche Eikrem; Wenche Eikrem 2Department of Biosciences, University of Oslo, P.O. Box 1066, Blindern, N-0316 Oslo, Norway3Norwegian Institute for Water Research, Gaustadalléen 21, 0349 Oslo, Norway Search for other works by this author on: GSW Google Scholar Elisabeth Alve Elisabeth Alve 1Department of Geosciences, University of Oslo, P.O. Box 1047 Blindern, 0316 Oslo, Norway Search for other works by this author on: GSW Google Scholar Journal of Foraminiferal Research (2014) 44 (4): 416–433. https://doi.org/10.2113/gsjfr.44.4.416 Article history received: 30 Aug 2013 accepted: 04 Apr 2014 first online: 03 Mar 2017 Cite View This Citation Add to Citation Manager Share Icon Share Facebook Twitter LinkedIn MailTo Tools Icon Tools Get Permissions Search Site Citation Christopher J. Duffield, Bente Edvardsen, Wenche Eikrem, Elisabeth Alve; EFFECTS OF DIFFERENT POTENTIAL FOOD SOURCES ON UPPER-BATHYAL BENTHIC FORAMINIFERA: AN EXPERIMENT WITH PROPAGULES. Journal of Foraminiferal Research 2014;; 44 (4): 416–433. doi: https://doi.org/10.2113/gsjfr.44.4.416 Download citation file: Ris (Zotero) Refmanager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentBy SocietyJournal of Foraminiferal Research Search Advanced Search Abstract A propagule experiment was designed to investigate the effects of different food types and varying sediment depths on the survival and growth of upper-bathyal benthic foraminifera, collected from surface-sediment cores in Oslofjord, Norway. Sediment that passed through a 53-μm sieve was used in the experiment. Any foraminifera >63 μm at the end of the experiment had therefore grown, indicating at least tolerable living conditions. The experiment was arranged into four sub-experiments to test foraminiferal responses to a lack of food input, algal medium, sediment depth (1- vs. 2-cm depth), and different food types. Potential food sources included monospecific algal cultures (the green alga Dunaliella tertiolecta, the haptophyte Emiliania huxleyi, and the diatoms Chaetoceros sp. and cf. Navicula), as well as phytoplankton and zooplankton from net hauls collected at the same sampling site. After six weeks all foraminiferal assemblages showed an increase in abundance, even those which were not fed. This suggests that most species (e.g., Textularia earlandi, Bathysiphon flexilis) were feeding on microbes or detritus already in the sediment. However, the addition of certain phytodetritus increased the abundance, suggesting that some species (e.g., Epistominella vitrea) are dependent on the input of this particular fresh phytodetritus. Conversely, certain types of detritus (E. huxleyi and zooplankton) appear detrimental to most species, except Elphidium excavatum which appeared resistant to the treatments inimicable to other species. Leptohalysis catella was the only species observed to respond positively to net hauls dominated by dinoflagellates. For some species (e.g., Stainforthia fusiformis, Nonionella iridea) the availability of a greater sediment depth stimulates growth more than the input of organic matter. You do not have access to this content, please speak to your institutional administrator if you feel you should have access.

Interaction of CdSe/ZnS quantum dots with the marine diatom Phaeodactylum tricornutum and the green alga Dunaliella tertiolecta: A biophysical approach

In this study, we investigated the interaction of nanoparticles, such as CdSe/ZnS quantum dots (QDs), with the marine diatom Phaeodactylum tricornutum and the green alga Dunaliella tertiolecta, as biological models in the marine environment. Fluorescence kinetics measurements indicated that 30min after dispersion in seawater QDs lost the 60% of the initial emission intensity, possibly due to the occurrence of aggregation processes. However, the presence of algae seemed to mitigate this effect. By using confocal microscopy, we highlighted the presence of QDs adsorbed on the surface of both algae, but not inside the cells. The toxicity of QDs was evaluated in terms of inhibition of growth rate, oxidative stress, and lipid peroxidation. QDs in the range of 1–2.5nM gradually inhibited the growth rate of P. tricornutum and increased the oxidative stress, as evinced by the increase in lipid peroxidation, reactive oxygen species (ROS) production and activity of two main antioxidant enzymes (superoxide dismutase and catalase). On the contrary, QDs did not inhibit the growth rate of D. tertiolecta, at most a modest stimulation was observed in the range of 0.5–2nM, suggesting a hormetic response. No effect in the parameters indicating oxidative stress was observed in the green alga. In conclusion our results showed that the biological effects were species-specific.

Production of recombinant enzymes in the marine alga Dunaliella tertiolecta

Photosynthetic marine algae are attractive targets for the production of biofuels and bio-products because they have the ability to capture and fix carbon dioxide using solar energy and they grow in seawater, thereby minimizing fresh water usage. Algae are a large and diverse group and transformation of algal chloroplasts has been limited to very few examples, mainly the model freshwater alga, Chlamydomonas reinhardtii. However, the potential for metabolic engineering and recombinant protein production using algal chloroplasts has been well demonstrated in this model species. Here we report the transformation of the chloroplast of the marine green alga Dunaliella tertiolecta. D. tertiolecta is an ideal species for biofuel production because it can maintain relatively high growth rates in a wide range of pH and salt concentrations, and because it contains relatively high lipid content. Here we show that transformation of the chloroplast of D. tertiolecta can occur by homologous recombination and selection for resistance to the antibiotic erythromycin using the erythromycin esterase gene, ereB. We successfully produce measurable quantities of five different classes of recombinant enzymes; xylanase, α-galactosidase, phytase, phosphate anhydrolase, and β-mannanase, in the plastids of D. tertiolecta or C. reinhardtii. This was achieved by transforming the plastid of D. tertiolecta via particle bombardment using a D. tertiolecta psbD promoter with 5′ UTR and psbA terminator with 3′ UTR to drive stable expression of codon optimized transgenes. Similar strategies should allow for recombinant protein production in many species of marine algae.

Growth of Dunaliella tertiolecta and associated bacteria in photobioreactors

The aim of this study was to test three flat-plate photobioreactor configurations for cultivation of marine green alga Dunaliella tertiolecta under non-axenic growth conditions and to characterize and quantify the associated bacteria. The photobioreactor cultivations were conducted using tap water-based media. Static mixers intended to enhance mixing and light utilization did not generally increase algal growth at the low light intensities used. The maximum biomass concentration (measured as volatile suspended solids) and maximum specific growth rate achieved in the flat plate with no mixer were 2.9 g l⁻¹ and 1.3 day⁻¹, respectively. Based on quantitative polymerase chain reaction, bacterial growth followed the growth of D. tertiolecta. Based on 16S rDNA amplification and denaturing gradient gel electrophoresis profiling, heterotrophic bacteria in the D. tertiolecta cultures mainly originated from the non-axenic algal inocula, and tap water heterotrophs were not enriched in high chloride media (3 % salinity). Bacterial communities were relatively stable and reproducible in all flat-plate cultivations and were dominated by Gammaproteobacteria, Flavobacteria, and Alphaproteobacteria.

Bioavailability of sediment-bound and algal metals to killifish Fundulus heteroclitus

We used a radiotracer technique to experimentally assess whether As(V), Cd, Cr(III), Hg(II), and methylmercury (MeHg) bound to sediment from 3 contaminated field sites (Baltimore Harbor, Elizabeth River, and Mare Island) and the green alga Dunaliella tertiolecta are bioavail- able to killifish Fundulus hetero clitus. Algae are a component of the killifish diet in salt marshes, and although killifish do not actively consume sediment, some is accidentally ingested due to attachment to benthic prey. For both sediment and algae, the assimilation efficiencies (AE) of ingested metals were highest for MeHg, followed by Hg(II), As, and Cd, and lowest for Cr. Follow- ing sediment intubations, AE values ranged from 0.01�0.03% (Cr) to 10�14% (MeHg), and ranged from 0.7% (Cr) to 82% (MeHg) following algal intubation. Following sediment intubations, loss rate constants (kef) were similar for As, Cd, and Hg(II) and lowest for MeHg, whereas following algal intubation, the kef values were highest for As, followed by Cr, Hg(II), and Cd, and lowest for MeHg. At the end of depuration, tissue distribution data showed that Cd and Hg(II) remained pri- marily associated with the viscera, whereas As and MeHg were distributed throughout the body. Calculated trophic transfer factors (TTF) showed that only MeHg bound to algae, and Elizabeth River sediment is expected to biomagnify at this trophic step (TTF > 1). Metals can accumulate to high concentrations in sediment in industrialized coastal areas, but the present study indicates that the risk of exposure for killifish from ingesting contaminated sediment is minimal.