ABSTRACT
Paralytic shellfish poisoning (PSP) toxins are secondary metabolites of the toxic species of phytoplankton. The consumption of shellfish accumulating these toxins can cause neurological symptoms and even death. Within the framework of the surveillance program of seafood safety along the Moroccan littoral environment established by National Institute of Fisheries Research (INRH), a study of PST was conducted from 2004 to 2016 in south Moroccan’s shellfish, mussels from south Agadir region and Razor Shell from Dakhla bay. The surveillance was carried out bi-monthly or weekly using the AOAC official method of analysis (AOAC 959.08) mouse bioassay (MBA). In parallel, monitoring of toxic phytoplankton in water was conducted. With the aim to determine the shellfish toxin profile, ion-pair high-performance liquid chromatography with post-column derivatisation and fluorescence detection (HPLC-FD) was performed. The Receptor Binding Assay (RBA) also was used for determination of total toxicity of PSP toxins in Agadir’s mussels.In both regions, the analysis of seawater revealed the presence of the toxic algae Alexandrium spp during toxics events. Along the coast of Agadir, PSP toxins in shellfish were associated with the presence of Alexandrium cf. minutum in seawater. These toxic events were widely distributed in time and space and mainly detected during the summer and fall seasons. In some samples concentrations exceeded the sanitary threshold (ST) of 800 ?g eq STX /kg. HPLC analysis revealed that Saxitoxin and Gonyautoxins dominated the toxin profile. The comparison between different methods showed a strong uphill (positive) linear relationship, with a coefficient correlation of r=0.79 between MBA and HPLC and r = 0.809 between MBA and RBA
ABSTRACT
Aims: Several harmful dinoflagellate species are widely found in Malaysian marine waters. These microalgae are capable of producing a variety of toxins that can intoxicate humans through consumption of contaminated seafood. Therefore, the present work aimed to investigate the potential of a marine bacterium sdPS-7 isolate as a biological control agent against Alexandrium minutum KB-5. Methodology and results: The isolate sdPS-7 was obtained from marine sediments in Malaysia and examined for its algicidal activity toward the toxic dinoflagellate A. minutum KB-5 in laboratory culture. Based on morphological and molecular characterization, this isolate was identified as Aeromonas hydrophila sdPS-7. Alexandrium minutum KB-5 cultures were exposed to cell free bacteria culture filtrate and the effect on dinoflagelate growth was evaluated based on direct cell counts in the treated samples compared to non-treated control cultures. The bacterial filtrate was treated at different temperatures, salinities and exposed to repeated freezing and thawing five times to study its algicidal activity stability thereafter. The results showed a potent inhibition of the growth of A. minutum KB-5. The strongest effect was observed when the bacterium culture filtrate was mixed with A. minutum KB-5 cultures that were in lag phase, resulting in 99% or higher mortality. The cell-free filtrate proved to be heat- stable when exposed to temperatures of 2 °C to 100 °C for one hour each. There was also no substantial salinity as well as (freezing – thawing) effect on the filtrate algicidal activity. Conclusion, significance and impact of study: This study illustrated the potential use of the marine bacterial Aeromonas hydrophila sdPS-7 filtrates in controlling the growth of the toxic dinoflagellate A. minutum KB-5.
Subject(s)
Biological Control Agents , Aeromonas hydrophilaABSTRACT
En el presente trabajo se registra por primera vez al dinoflagelado potencialmente tóxico Alexandrium minutum Halim 1960 causante de las floraciones algales de marzo del 2006 y febrero del 2009, en el en el litoral del Callao, Perú. La identificación de A. minutum se realizó mediante un examen morfo-taxonómico detallando sus placas con microscopía de luz y epifluorescencia. Para su cuantificación se utilizaron cámaras de sedimentación. Nuestros resultados reportan por primera vez la presencia de A. minutum en el lado sudamericano del Pacífico, frente al Callao. Las características en tamaño, forma y morfología tecal que exhibieron los especímenes fueron muy similares a las descripciones clásicas de esta especie.
Herein, we report the first record of the potentially toxic dinoflagellate Alexandrium minutum Halim 1960 from the Peruvian littoral. Alexandrium minutum produced the algae bloom in March 2006 and February 2009, in the Callao bay. Its identification was carried out by a morpho-taxonomic examination, detailing their plates with light and epifluorescence microscopy, moreover its quantification was realized in sedimentation chambers. This is the first report of A. minutum for Southeast Pacific. The characteristics in size, shape and thecal morphology were similarly to original descriptions of this species.
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Aim of present study is to evaluate the effect of salinity on the growth of Rhizobium symbiosis with various cultivars of Berseem (WARDAN, BB3, JHB 052 and BB2). Two sets of plots were maintained in which one set contained non-inoculated while another set contained inoculated seeds with Rhizobium culture, which were irrigated with saline waters of different concentrations (0, 3, 6, 7.2, 10, 12 and 14 dSm-1). The observations have been recorded only at 90 and 120 DAS but nodular leghaemoglobin had been estimated at 90th day stage. Results indicated that nodulation and lb content had been increased generally upto 7.2 dSm-1 and declined thereafter. Inoculation with Rhizobium culture had invariably and significantly promoted nodulation and lb content at both durations particularly at lower EC levels and minimized the deleterious effect of salinity at 10 to 14 dSm-1. Taken together, our findings indicate that cv. BB3 produced maximum nodulation and lb content almost at all saline irrigations but cv. WARDAN registered beneficial effect of Rhizobium culture inoculation as this cultivar registered greater lb content at 3 to 7.2 dSm-1 and lesser reductions at 10 to 14 dSm-1 when compared with uninoculated sets. We concluded that this experiment reveals the great impact of Rhizobium trifolii culture on berseem cultivars along with the use of saline soil and water for agriculture without using fertile land and normal water, hence there will be a substantial conservation of normal water and soil for further use.
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Objective To study on algicidal bioactive substances from mangrove bacteria and its algicidal effect on red tide algae Alexandriam tamarense.Methods A red algicidal bioactive substance in Guangxi mangrove bacteria was isolated and purified by Silica-gel Column Chromatography,and its structure was determined on the basis of UV,IR,1H NMR,13C NMR and HREIMS spectroscopic analyses and comparison with the literatures.Its algicidal affect was primarily studied in this paper.Results and Conelusion The results showed that the red algicidal bioactive substance was prodigiosin,which had an inhibitory effect on the cells growth of Alexandrium tamarense,and the inhibitory effect increased with the increase of prodigiosin concentration.The prodigiosin stimulated the production of MDA and reduced the content of sulfhydryl group.In addition,plasma membrane permeability of leaked cell solution was increased.These indicated the extinguishing mechanism: the cell membrane was damaged followed by the inhibition of the cell growth.
ABSTRACT
ve To study the growth curve of Alexandrium tamarense and the toxicity of paralytic shelfish poisoning(PSP) selected in different growth phases, as well as to quantitatively analyze the toxins and compare the different efficiency of breaking cell wall and their virtues and defects between freezing-thawing method and supersonic method, and to provide theoretical basis for the selection of the methods for extraction of PSP. Methods Cells were collected by suction filter, cell wall was broken by freezing-thawing method and supersonic method, the toxicities of Alexandrium tamarense among different growth phases were detected and compared. Results The growth of Alexandrium tamarense typically showed three phases which included a lag phase(0~9 days), an exponential growth phase(10~18 days), and a stationary phase(19~22 days) . The maximum toxicity of cells in the stationary phase appeared, especially in day 21 when the population of cells reached to 9.43?10-6 MU/cell, although the cells in the exponential phase grew fastest. Toxicity of the cells in the lag phase broken by freezing-thawing method was more stronger than that by supersonic method, that meant the toxicity of cells was lowered after the supersonic treatment. In additional, the filtering method for collecting cells presented a lower recovery rate of average 69.0% . Conclusion As for the comparing of freezing-thawing method and supersonic method, it was found that, when cells were in the same phase, the supersonic method had remarkable advantages, but it also had the disadvantage of lowering the tox-icity of cells. When in the same condition of growth and method of fragmentation, cells in the lag phase were broken most easily, and cells in the stationary phase were more difficult to be broken than those in the other two phases. Toxicity of cells was larger and larger with the time of incubation. The toxicity of cells in the lag phase had reached a higher intensity, although toxicities of cells in the next two phases would increase a little.