Publications by authors named "Mengmeng Tong"

17 Publications

  • Page 1 of 1

Hemolytic Activity in Relation to the Photosynthetic System in and .

Mar Drugs 2021 Jun 12;19(6). Epub 2021 Jun 12.

Key Laboratory of Aquatic Eutrophication and Control of Harmful Algal Blooms of Guangdong Higher Education Institute, Research Center of Hydrobiology, Jinan University, Guangzhou 510632, China.

species, and , are harmful raphidophycean flagellates known to have hemolytic effects on many marine organisms and resulting in massive ecological damage worldwide. However, knowledge of the toxigenic mechanism of these ichthyotoxic flagellates is still limited. Light was reported to be responsible for the hemolytic activity (HA) of species. Therefore, the response of photoprotective, photosynthetic accessory pigments, the photosystem II (PSII) electron transport chain, as well as HA were investigated in non-axenic and cultures under variable environmental conditions (light, iron and addition of photosynthetic inhibitors). HA and hydrogen peroxide (HO) were quantified using erythrocytes and pHPA assay. Results confirmed that% HA of was initiated by light, but was not always elicited during cell division. Exponential growth of and under the light over 100 µmol m s or iron-sufficient conditions elicited high hemolytic activity. Inhibitors of PSII reduced the HA of , but had no effect on . The toxicological response indicated that HA in was not associated with the photoprotective system, i.e., xanthophyll cycle and regulation of reactive oxygen species, nor the PSII electron transport chain, but most likely occurred during energy transport through the light-harvesting antenna pigments. A positive, highly significant relationship between HA and chlorophyll (chl) biosynthesis pigments, especially chl and chl , in both species, indicated that hemolytic toxin may be generated during electron/energy transfer through the chl biosynthesis pathway.
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http://dx.doi.org/10.3390/md19060336DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8231601PMC
June 2021

Sulfamethoxazole induced systematic and tissue-specific antioxidant defense in marine mussels (Mytilus galloprovincialis): Implication of antibiotic's ecotoxicity.

Chemosphere 2021 Sep 22;279:130634. Epub 2021 Apr 22.

Institute of Marine Biology and Pharmacology, Ocean College, Zhejiang University, Zhoushan, 316000, China. Electronic address:

Sulfamethoxazole (SMX), recognized as emerging pollutant, has been frequently detected in aquatic environment. However, effects induced by SMX and the underneath mechanism on non-target aquatic organisms, marine mussels (Mytilus galloprovincialis), are still largely unknown. In present study, marine mussels were exposed to SMX (nominal concentrations 0.5, 50 and 500 μg/L) for 6 days, followed by 6 days depuration and responses of antioxidant defenses, e.g. superoxide dismutase (SOD), catalase (CAT) and glutathione-S-transferase (GST), etc., at transcriptional, translational and functional levels were evaluated in two vital tissues, gills and digestive glands. Results showed SMX can be accumulated in mussels while the bio-accumulative ability was low under the experimental condition. A systemic but not completely synchronous antioxidant defense at different levels upon SMX exposure. The transcriptional alteration was more sensitive and had the potential to be used as early warning of SMX induced ecotoxicity. Complementary function of antioxidant enzymes with specific alteration of metabolism related gene (gst) suggested that further researches should focused on SMX metabolism and SMX induced effects simultaneously. Significant tissue-specific antioxidant responses were discovered and gills showed earlier and quicker reacting ability than digestive glands, which was closely related to the functional diversity and different thresholds of xenobiotics allowance.
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http://dx.doi.org/10.1016/j.chemosphere.2021.130634DOI Listing
September 2021

Effect of allelochemicals on photosynthetic and antioxidant defense system of Ulva prolifera.

Aquat Toxicol 2020 Jul 16;224:105513. Epub 2020 May 16.

University of Maryland Center for Environment Science, Horn Point Laboratory, Cambridge, MD, 21613, USA.

Ulva prolifera is a macroalgae that forms massive blooms, negatively impacting natural communities, aquaculture operations and recreation. The effects of the natural products, eugenol, β-myrcene, citral and nonanoic acid on the growth rate, antioxidative defense system and photosynthesis of Ulva prolifera were investigated as a possible control strategy for this harmful taxon. Negative effects on growth were observed with all four chemicals, due to the excessive production of reactive oxygen species and oxidative damage to the thalli. However, the response of U. prolifera under the four chemicals stress was different at the cellular level. β-myrcene, the most effective compound in terms of growth inhibition, induced oxidative stress as shown by the damage of total antioxidant capacity (T-AOC) and the downregulation of the glutathione-ascorbate (GSH-ASA) cycle which inhibited the antioxidative system. This chemical also inhibited photosynthesis and photoprotection mechanisms in U. prolifera, resulting in growth limitation. In contrast, U. prolifera was less affected by the second tested chemical, eugenol, and showed no significant change on photosynthetic efficiency in the presence of the chemical. The inhibition effects of the third and fourth tested chemicals, nonanoic acid and citralon, on growth and on the antioxidant defense system in U. prolifera were inferior. These results provide a potential avenue for controlling green tides in the future.
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http://dx.doi.org/10.1016/j.aquatox.2020.105513DOI Listing
July 2020

Cell cycle regulation of the mixotrophic dinoflagellate Dinophysis acuminata: Growth, photosynthetic efficiency and toxin production.

Harmful Algae 2019 11 11;89:101672. Epub 2019 Oct 11.

Biology Department, Woods Hole Oceanographic Institute, Woods Hole, MA, 02543, USA.

The mixotrophic dinoflagellate Dinophysis acuminata is a widely distributed diarrhetic shellfish poisoning (DSP) producer. Toxin variability of Dinophysis spp. has been well studied, but little is known of the manner in which toxin production is regulated throughout the cell cycle in these species, in part due to their mixotrophic characteristics. Therefore, an experiment was conducted to investigate cell cycle regulation of growth, photosynthetic efficiency, and toxin production in D. acuminata. First, a three-step synchronization approach, termed "starvation-feeding-dark", was used to achieve a high degree of synchrony of Dinophysis cells by starving the cells for 2 weeks, feeding them once, and then placing them in darkness for 58 h. The synchronized cells started DNA synthesis (S phase) 10 h after being released into the light, initiated G2 growth stage eight hours later, and completed mitosis (M phase) 2 h before lights were turned on. The toxin content of three dominant toxins, okadaic acid (OA), dinophysistoxin-1 (DTX1) and pectenotoxin-2 (PTX2), followed a common pattern of increasing in G1 phase, decreasing on entry into the S phase, then increasing again in S phase and decreasing in M phase during the diel cell cycle. Specific toxin production rates were positive throughout the G1 and S phases, but negative during the transition from G1 to S phase and late in M phase, the latter reflecting cell division. All toxins were initially induced by the light and positively correlated with the percentage of cells in S phase, indicating that biosynthesis of Dinophysis toxins might be under circadian regulation and be most active during DNA synthesis.
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http://dx.doi.org/10.1016/j.hal.2019.101672DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6914227PMC
November 2019

Phosphorus-Induced Lipid Class Alteration Revealed by Lipidomic and Transcriptomic Profiling in Oleaginous Microalga sp. PJ12.

Mar Drugs 2019 Sep 3;17(9). Epub 2019 Sep 3.

School of Marine Science and Technology, Zhejiang Ocean University, Zhoushan 316022, China.

Phytoplankton are primary producers in the marine ecosystem, where phosphorus is often a limiting factor of their growth. Hence, they have evolved strategies to recycle phosphorus by replacing membrane phospholipids with phosphorus-free lipids. However, mechanisms for replacement of lipid classes remain poorly understood. To improve our understanding, we performed the lipidomic and transcriptomic profiling analyses of an oleaginous marine microalga sp. PJ12 in response to phosphorus depletion (PD) and replenishing. In this study, by using (liquid chromatography couple with tandem mass spectrometry) LC-MS/MS-based lipidomic analysis, we show that membrane phospholipid levels are significantly reduced upon PD, while phosphorus-free betaine lipid levels are increased. However, levels of phosphorus-free photosynthetic galactolipid and sulfolipid are not increased upon PD, consistent with the reduced photosynthetic activity. RNA-seq-based transcriptomic analysis indicates that enzymes involved in phospholipid recycling and phosphorus-free lipid synthesis are upregulated, supporting the lipidomic analysis. Furthermore, enzymes involved in FASII (type II fatty acid synthesis) elongation cycle upon PD are transcriptionally downregulated. EPA (eicosapentaenoic acid) level decrease upon PD is revealed by both GC-MS (gas chromatography coupled with mass spectrometry) and LC-MS/MS-based lipidomic analyses. PD-induced alteration is reversed after phosphorus replenishing. Taken together, our results suggest that the alteration of lipid classes upon environmental change of phosphorus is a result of remodeling rather than de novo synthesis in sp. PJ12.
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http://dx.doi.org/10.3390/md17090519DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6780086PMC
September 2019

Prey Lysate Enhances Growth and Toxin Production in an Isolate of .

Toxins (Basel) 2019 01 21;11(1). Epub 2019 Jan 21.

Virginia Institute of Marine Science, College of William & Mary, Gloucester Point, VA 23062, USA.

The physiological and toxicological characteristics of have been increasingly studied in an attempt to better understand and predict diarrhetic shellfish poisoning (DSP) events worldwide. Recent work has identified prey quantity, organic nitrogen, and ammonium as likely contributors to increased growth rates and/or toxicity. Further research is now needed to better understand the interplay between these factors, for example, how inorganic and organic compounds interact with prey and a variety of species and/or strains. In this study, the exudate of ciliate prey and cryptophytes were investigated for an ability to support growth and toxin production in the presence and absence of prey, i.e., during mixotrophic and phototrophic growth respectively. A series of culturing experiments demonstrated that the addition of ciliate lysate led to faster dinoflagellate growth rates (0.25 ± 0.002/d) in predator-prey co-incubations than in treatments containing (1) similar levels of prey but without lysate (0.21 ± 0.003/d), (2) ciliate lysate but no live prey (0.12 ± 0.004/d), or (3) monocultures of without ciliate lysate or live prey (0.01 ± 0.007/d). The addition of ciliate lysate to co-incubations also resulted in maximum toxin quotas and extracellular concentrations of okadaic acid (OA, 0.11 ± 0.01 pg/cell; 1.37 ± 0.10 ng/mL) and dinophysistoxin-1 (DTX1, 0.20 ± 0.02 pg/cell; 1.27 ± 0.10 ng/mL), and significantly greater total DSP toxin concentrations (intracellular + extracellular). Pectenotoxin-2 values, intracellular or extracellular, did not show a clear trend across the treatments. The addition of cryptophyte lysate or whole cells, however, did not support dinoflagellate cell division. Together these data demonstrate that while certain growth was observed when only lysate was added, the benefits to were maximized when ciliate lysate was added with the ciliate inoculum (i.e., during mixotrophic growth). Extrapolating to the field, these culturing studies suggest that the presence of ciliate exudate during co-occurring dinoflagellate-ciliate blooms may indirectly and directly exacerbate abundance and toxigenicity. More research is required, however, to understand what direct or indirect mechanisms control the predator-prey dynamic and what component(s) of ciliate lysate are being utilized by the dinoflagellate or other organisms (e.g., ciliate or bacteria) in the culture if predictive capabilities are to be developed and management strategies created.
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http://dx.doi.org/10.3390/toxins11010057DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6356360PMC
January 2019

Impact of Feeding on Nutrient Dynamics and Bacterial Composition in a Microcosm.

Toxins (Basel) 2018 Oct 30;10(11). Epub 2018 Oct 30.

Ocean College, Zhejiang University, No 1 Zheda Road, Zhoushan 316000, Zhejiang, China.

The development of populations, producers of diarrhetic shellfish toxins, has been attributed to both abiotic (e.g., water column stratification) and biotic (prey availability) factors. An important process to consider is mixotrophy of the species, which is an intensive feeding of the species for nutrients and a benefit from kleptochloroplasts. During the feeding process, the nutritional status in the environment changes due to the preference of and/or for different nutrients, prey cell debris generated by sloppy feeding, and their degradation by micro-organisms changes. However, there is little knowledge about the role of the bacterial community during the co-occurrence of and and how they directly or indirectly interact with the mixotrophs. In this study, laboratory experiments were performed to characterize the environmental changes including those of the prey present, the bacterial communities, and the ambient dissolved nutrients during the co-occurrence of and . The results showed that, during the incubation of the ciliate prey with its predator , available dissolved nitrogen significantly shifted from nitrate to ammonium especially when the population of decayed. Growth phases of and greatly affected the structure and composition of the bacterial community. These changes could be mainly explained by both the changes of the nutrient status and the activity of cells. feeding activity also accelerated the decline of and contamination of cultures with okadaic acid, dinophysistoxin-1, and pectenotoxin-2, but their influence on the prokaryotic communities was limited to the rare taxa (<0.1%) fraction. This suggests that the interaction between and bacteria is species-specific and takes place intracellularly or in the phycosphere. Moreover, a majority of the dominant bacterial taxa in our cultures may also exhibit a metabolic flexibility and, thus, be unaffected taxonomically by changes within the culture system.
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http://dx.doi.org/10.3390/toxins10110443DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6266072PMC
October 2018

Analysis of multiple pesticide residues in polyphenol-rich agricultural products by UPLC-MS/MS using a modified QuEChERS extraction and dilution method.

Food Chem 2019 Feb 31;274:452-459. Epub 2018 Aug 31.

State Key Laboratory of Tea Plant Biology and Utilization, International Joint Laboratory on Tea Chemistry and Health Effects, School of Tea and Food Science & Technology, Anhui Agricultural University, Anhui Province Key Lab of Analysis and Detection for Food Safety, Hefei 230036, PR China. Electronic address:

An efficient method for the rapid extraction and clean-up of 20 pesticide residues from polyphenol-rich agricultural samples (tea, apple, broccoli, and shallot) for analysis by UPLC-MS/MS was developed. Following extraction, PVPP was used to precipitate polyphenols, supernatant was diluted to minimize matrix effects. Homogenized samples were vortexed in acetonitrile prior to cleanup with a combination of PVPP (150 mg), PSA (50 mg) and GCB (10 mg). Supernatant (1 mL) was filtered and diluted 10-fold before analysis. In 4 agricultural products that usually produce high interference, the matrix effects were overcome for all pesticides expect in green and oolong tea for acephate, omethoate, dinotefuran and nitenpyram. Mean recoveries ranged from 73% to 106%, and RSD ≦ 13%. Limits of quantification ranged from 0.01 to 0.02 mg kg. PVPP as one of excellent QuEChERS material combined with dilution was verified as a promising method for multiple pesticide residues analysis in complex matrices.
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http://dx.doi.org/10.1016/j.foodchem.2018.08.134DOI Listing
February 2019

Effect of ciliate strain, size, and nutritional content on the growth and toxicity of mixotrophic Dinophysis acuminata.

Harmful Algae 2018 09 18;78:95-105. Epub 2018 Aug 18.

Woods Hole Oceanographic Institution, Biology Department, Woods Hole, MA, 02543, USA. Electronic address:

Previous studies indicate differences in bloom magnitude and toxicity between regional populations, and more recently, between geographical isolates of Dinophysis acuminata; however, the factors driving differences in toxicity/toxigenicity between regions/strains have not yet been fully elucidated. Here, the roles of prey strains (i.e., geographical isolates) and their associated attributes (i.e., biovolume and nutritional content) were investigated in the context of growth and production of toxins as a possible explanation for regional variation in toxicity of D. acuminata. The mixotrophic dinoflagellate, D. acuminata, isolated from NE North America (MA, U.S.) was offered a matrix of prey lines in a full factorial design, 1 × 2 × 3; one dinoflagellate strain was fed one of two ciliates, Mesodinium rubrum, isolated from coastal regions of Japan or Spain, which were grown on one of three cryptophytes (Teleaulax/Geminigera clade) isolated from Japan, Spain, or the northeastern USA. Additionally, predator: prey ratios were manipulated to explore effects of the prey's total biovolume on Dinophysis growth or toxin production. These studies revealed that the biovolume and nutritional status of the two ciliates, and less so the cryptophytes, impacted the growth, ingestion rate, and maximum biomass of D. acuminata. The predator's consumption of the larger, more nutritious prey resulted in an elevated growth rate, greater biomass, and increased toxin quotas and total toxin per mL of culture. Grazing on the smaller, less nutritious prey, led to fewer cells in the culture but relatively more toxin exuded from the cells on per cell basis. Once the predator: prey ratios were altered so that an equal biovolume of each ciliate was delivered, the effect of ciliate size was lost, suggesting the predator can compensate for reduced nutrition in the smaller prey item by increasing grazing. While significant ciliate-induced effects were observed on growth and toxin metrics, no major shifts in toxin profile or intracellular toxin quotas were observed that could explain the large regional variations observed between geographical populations of this species.
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http://dx.doi.org/10.1016/j.hal.2018.08.001DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6178807PMC
September 2018

Uptake, Translocation, Metabolism, and Distribution of Glyphosate in Nontarget Tea Plant (Camellia sinensis L.).

J Agric Food Chem 2017 Sep 21;65(35):7638-7646. Epub 2017 Aug 21.

State Key Laboratory of Tea Plant Biology and Utilization; International Joint Laboratory on Tea Chemisty and Health Effects, School of Tea and Food Science & Technology, Anhui Agricultural University , Hefei 230036, P. R. China.

The uptake, translocation, metabolism, and distribution behavior of glyphosate in nontarget tea plant were investigated. The negative effects appeared to grown tea saplings when the nutrient solution contained glyphosate above 200 mg L. Glyphosate was highest in the roots of the tea plant, where it was also metabolized to aminomethyl phosphonic acid (AMPA). The glyphosate and AMPA in the roots were transported through the xylem or phloem to the stems and leaves. The amount of AMPA in the entire tea plant was less than 6.0% of the amount of glyphosate. The glyphosate level in fresh tea shoots was less than that in mature leaves at each day. These results indicated that free glyphosate in the soil can be continuously absorbed by, metabolized in, and transported from the roots of the tea tree into edible leaves, and therefore, free glyphosate residues in the soil should be controlled to produce teas free of glyphosate.
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http://dx.doi.org/10.1021/acs.jafc.7b02474DOI Listing
September 2017

Investigation of degradation and penetration behaviors of dimethoate on and in spinach leaves using in situ SERS and LC-MS.

Food Chem 2017 Dec 23;237:305-311. Epub 2017 May 23.

Department of Food Science, University of Massachusetts, Amherst, MA, USA. Electronic address:

To investigate the degradation and penetration behaviors of the organophosphate insecticide dimethoate applied on spinach leaves, in situ SERS and LC-MS methods were used to detect dimethoate residue on&in spinach leaves picked on different days after treatment (DAT). The SERS and LC-MS methods determined that the dimethoate degradation rate followed first-order kinetics, with a half-life of 3.56 or 4.13days, depending on the respective method. The correlation coefficient of quantification value of these two methods was 0.9562. With the SERS method, we detected most of the penetrated dimethoate in the depth of 60-110μm. With the LC-MS method, we detected dimethoate up to 0.17ng in leaves and that the dimethoate on:in ratio of spinach leaves ranged from 562.25 on 0 DAT to 5.23 on 14 DAT. The combination of these two methods facilitated a better understanding of the behavior and biological fate of pesticides in a complex biological system.
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http://dx.doi.org/10.1016/j.foodchem.2017.05.117DOI Listing
December 2017

Rates of nitrogen uptake by cyanobacterially-dominated assemblages in Lake Taihu, China, during late summer.

Harmful Algae 2017 05 6;65:71-84. Epub 2017 May 6.

Ocean College, Zhejiang University, Zhoushan, 316021, China; Laboratory of Marine Ecosystem and Biogeochemistry, Second Institute of Oceanography, State Oceanographic Administration, Hangzhou, 310012, China. Electronic address:

Lake Taihu has suffered an increasing number of cyanobacteria harmful algal blooms (CyanoHABs) over the past three decades, bringing about formidable ecological and economical losses. Efforts to control phosphate (P) and/or nitrogen (N) have been applied to mitigate these blooms, but there has been much less attention paid to N and its different forms on the ecology of the blooms. Therefore, kinetic and nutrient enrichment experiments were conducted to assess N uptake rates under differing conditions, and to examine effects of changes in N forms (NH, NO and urea) and P availability on phytoplankton community physiology. In 2014 these experiments involved mesocosm enrichments; in 2015 these experiments were conducted over a diurnal period. Both involved measurements of short-term N uptake. The kinetic results showed that the utilization of NH, NO and urea by Microcystis-dominated communities was not efficient at low ambient substrate concentrations. Maximum uptake rates by these phytoplankton was achieved on NH and these rates were significantly higher than those on NO or urea with or without nutrient pretreatment. Moreover in the presence of PO enrichment, the maximal uptake velocity of NH substantially increased without evidence of saturation. High amounts of NH may have inhibited or repressed the uptake of NO at certain times in these studies. In the diurnal study, dissolved inorganic carbon and pH changed substantially throughout the day. The resulting high pH altered N and P in ways that may help to sustain nutrient cycling for the blooms.
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http://dx.doi.org/10.1016/j.hal.2017.04.001DOI Listing
May 2017

Optimized combination of dilution and refined QuEChERS to overcome matrix effects of six types of tea for determination eight neonicotinoid insecticides by ultra performance liquid chromatography-electrospray tandem mass spectrometry.

Food Chem 2016 Nov 22;210:26-34. Epub 2016 Apr 22.

School of Resource & Environment of Anhui Agricultural University, Key Lab. of Agri-food Safety of Anhui Province, Hefei 230036, PR China. Electronic address:

Liquid chromatography-electrospray ionization tandem mass spectrometry (LC-ESI-MS/MS) is a primary tool for analysis of low volatility compounds in complex matrices. However, complex matrices, such as different types of tea, complicate analysis through ionization suppression or enhancement. In this study, sample preparation by a refined QuEChERS method combined with a dilution strategy removed almost all matrix effects caused by six types of tea. Tea samples were soaked with water and extracted with acetonitrile, cleaned up with a combination of PVPP (160mg) and GCB (20mg), and dried. Dried extracts were diluted with 20mL acetonitrile/water (15:85, v/v) before analysis by UPLC-MS/MS. The average recoveries of eight neonicotinoid insecticides (dinotefuran, nitenpyram, thiamethoxam, imidacloprid, clothianidin, imidaclothiz, acetamiprid, and thiacloprid) ranged from 66.3 to 108.0% from tea samples spiked at 0.01-0.5mgkg(-1). Relative standard deviations were below 16% for all recovery tests. The limit of quantification ranged from 0.01 to 0.05mgkg(-1).
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http://dx.doi.org/10.1016/j.foodchem.2016.04.097DOI Listing
November 2016

Characterization and comparison of toxin-producing isolates of Dinophysis acuminata from New England and Canada.

J Phycol 2015 Feb 11;51(1):66-81. Epub 2014 Dec 11.

Biology Department and the Woods Hole Center for Oceans and Human Health, Woods Hole Oceanographic Institution, Woods Hole, Massachusetts, 02543, USA.

Following the identification of the first toxic isolate of Dinophysis acuminata from the northwestern Atlantic, we conducted detailed investigations into the morphology, phylogeny, physiology, and toxigenicity of three isolates from three sites within the northeastern U.S./Canada region: Eel Pond and Martha's Vineyard, Massachusetts, and the Bay of Fundy. Another isolate, collected from the Gulf of Mexico, was grown under the same light, temperature, and prey conditions for comparison. Despite observed phenotypic heterogeneity, morphometrics and molecular evidence classified the three northwestern Atlantic isolates as D. acuminata Claparède & Lachmann, whereas the isolate from the Gulf of Mexico was morphologically identified as D. cf. ovum. Physiological and toxin analyses supported these classifications, with the three northwestern Atlantic isolates being more similar to each other with respect to growth rate, toxin profile, and diarrhetic shellfish poisoning (DSP) toxin content (okadaic acid + dinophysistoxin 1/cell) than they were to the isolate from the Gulf of Mexico, which had toxin profiles similar to those published for D. cf. ovum F. Schütt. The DSP toxin content, 0.01-1.8 pg okadaic acid (OA) + dinophysistoxin (DTX1) per cell, of the three northwestern Atlantic isolates was low relative to other D. acuminata strains from elsewhere in the world, consistent with the relative scarcity of shellfish harvesting closures due to DSP toxins in the northeastern U.S. and Canada. If this pattern is repeated with the analyses of more geographically and temporally dispersed isolates from the region, it would appear that the risk of significant DSP toxin outbreaks in the northwestern Atlantic is low to moderate. Finally, the morphological, physiological, and toxicological variability within D. acuminata may reflect spatial (and/or temporal) population structure, and suggests that sub-specific resolution may be helpful in characterizing bloom dynamics and predicting toxicity.
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http://dx.doi.org/10.1111/jpy.12251DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5428078PMC
February 2015

Role of dissolved nitrate and phosphate in isolates of and toxin-producing .

Aquat Microb Ecol 2015 24;75(2):169-185. Epub 2015 Jun 24.

Biology Department, Woods Hole Oceanographic Institution, Woods Hole, MA 02543, USA.

, a producer of toxins associated with diarrhetic shellfish poisoning (DSP) and/or pectenotoxins (PTXs), is a mixotrophic species that requires both ciliate prey and light for growth. Linkages have been described in the literature between natural abundances of the predator and its prey, , and culture experiments have demonstrated that prey, in addition to light, is required for toxin production by ; together these suggest is a critical component for growth and toxicity. However, little is known about the role of dissolved inorganic nutrients on growth or that of toxin-producing . Accordingly, a series of experiments were conducted to investigate the possible uptake of dissolved nitrate and phosphate by 1) starved of prey, 2) feeding on , and 3) grown in nutritionally-modified media. All single-clone or mixed cultures were monitored for dissolved and particulate nutrient levels over the growth cycle, as well as growth rate, biomass, and toxin production when appropriate. did not utilize dissolved nitrate or phosphate in the medium under any nutrient regime tested, i.e., nutrient-enriched and nutrient-reduced, in the absence or presence of prey, or during any growth phase monitored, i.e., exponential and plateau phases. Changes in particulate phosphorus and nitrogen in , were instead, strongly influenced by the consumption of prey, and these levels quickly stabilized once prey were no longer available. , on the other hand, rapidly assimilated dissolved nitrate and phosphate into its particulate nutrient fraction, with maximum uptake rates of 1.38 pmol N/cell/day and 1.63 pmol P/cell/day. While did not benefit directly from the dissolved nitrate and phosphate, its growth (0.37±0.01 day) and toxin production rates for okadaic acid (OA), dinophysistoxin-1 (DTX1) or pectenotoxin-2 (PTX2), 0.1, 0.9 and 2.6 pg /cell/day, respectively, were directly coupled to prey availability. These results suggest that while dissolved nitrate and phosphate do not have a direct effect on toxin production or retention by , these nutrient pools contribute to prey growth and biomass, thereby indirectly influencing blooms and overall toxin in the system.
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http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5055077PMC
http://dx.doi.org/10.3354/ame01757DOI Listing
June 2015

Genomic reconstruction to improve bioethanol and ergosterol production of industrial yeast Saccharomyces cerevisiae.

J Ind Microbiol Biotechnol 2015 Feb 5;42(2):207-18. Epub 2014 Dec 5.

Zhejiang University, Zijingang Campus, 866 Yuhangtang Road, Hangzhou, 310058, Zhejiang, People's Republic of China.

Baker's yeast (Saccharomyces cerevisiae) is the common yeast used in the fields of bread making, brewing, and bioethanol production. Growth rate, stress tolerance, ethanol titer, and byproducts yields are some of the most important agronomic traits of S. cerevisiae for industrial applications. Here, we developed a novel method of constructing S. cerevisiae strains for co-producing bioethanol and ergosterol. The genome of an industrial S. cerevisiae strain, ZTW1, was first reconstructed through treatment with an antimitotic drug followed by sporulation and hybridization. A total of 140 mutants were selected for ethanol fermentation testing, and a significant positive correlation between ergosterol content and ethanol production was observed. The highest performing mutant, ZG27, produced 7.9 % more ethanol and 43.2 % more ergosterol than ZTW1 at the end of fermentation. Chromosomal karyotyping and proteome analysis of ZG27 and ZTW1 suggested that this breeding strategy caused large-scale genome structural variations and global gene expression diversities in the mutants. Genetic manipulation further demonstrated that the altered expression activity of some genes (such as ERG1, ERG9, and ERG11) involved in ergosterol synthesis partly explained the trait improvement in ZG27.
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http://dx.doi.org/10.1007/s10295-014-1556-7DOI Listing
February 2015

Toxin profiles of five geographical isolates of Dinophysis spp. from North and South America.

Toxicon 2011 Feb 10;57(2):275-87. Epub 2010 Dec 10.

U.S. Food and Drug Administration, Gulf Coast Seafood Laboratory, 1 Iberville Drive, Dauphin Island, AL 36528, USA.

Marine dinoflagellates of the genus Dinophysis can produce toxins of the okadaic acid (OA) and pectenotoxin (PTX) groups. These lipophilic toxins accumulate in filter-feeding shellfish and cause an illness in consumers called diarrhetic shellfish poisoning (DSP). In 2008, a bloom of Dinophysis led to the closure of shellfish harvesting areas along the Texas coast, one of the first DSP-related closures in the U.S. This event resulted in a broad study of toxin production in isolates of Dinophysis spp. from U.S. waters. In the present study, we compared toxin profiles in geographical isolates of Dinophysis collected in the U.S. (Eel Pond, Woods Hole MA; Martha's Vineyard, MA; and Port Aransas Bay, Texas), and in those from Canada (Blacks Harbour, Bay of Fundy) and Chile (Reloncavi Estuary), when cultured in the laboratory under the same conditions. For each isolate, the mitochondrial cox1 gene was sequenced to assist in species identification. Strains from the northeastern U.S. and Canada were all assigned to Dinophysis acuminata, while those from Chile and Texas were most likely within the D. acuminata complex whereas precise species designation could not be made with this marker. Toxins were detected in all Dinophysis isolates and each isolate had a different profile. Toxin profiles of isolates from Eel Pond, Martha's Vineyard, and Bay of Fundy were most similar, in that they all contained OA, DTX1, and PTX2. The Eel Pond isolate also contained OA-D8 and DTX1-D7, and low levels (unconfirmed structurally) of DTX1-D8 and DTX1-D9. D. acuminata from Martha's Vineyard produced DTX1-D7, along with OA, DTX1, and PTX2, as identified in both the cells and the culture medium. D. acuminata from the Bay of Fundy produced DTX1 and PTX2, as found in both cells and culture medium, while only trace amounts of OA were detected in the medium. The Dinophysis strain from Texas only produced OA, and the one from Chile only PTX2, as confirmed in both cells and culture medium.
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http://dx.doi.org/10.1016/j.toxicon.2010.12.002DOI Listing
February 2011
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