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Effects of non-toxic filamentous cyanobacteria isolated from tri an reservoir on Daphnia
Get PDFThis study is aimed to examine whether the presence of non-toxic filamentous cyanobacteria can cause toxic effects on Daphnia magna. Six strains of Oscillatoria perornata were isolated from the Tri An Reservoir and cultured in our laboratory for investigation. The results revealed that all strains were negative with the mcyA moleculer marker. The high performance liquid chromatography (HPLC) results showed that toxin was not detected in their culture products, indicating that these strains corresponded to non-toxin producing strains. However, the results of chronic assay indicated that these non-toxin producing O. perornata conferred toxic effects on the tested animals. The age at first reproduction of D. magna was delayed and the survival of D. manga decreased in proportional with the increase of the density of cells of O. perornata exposed. Significant differences in the life history responses were observed for D. mangna exposed to O. perornata. These results suggested that bioactive secondary metabolites other than microcystins produced by the filamentous cyanobacteria O. perornata may contribute to the toxic effects on Daphnia. Besides cyanotoxins, other secondary metabolites must be taken into account when investigating the toxic effects of cyanobacteria.
Investigation of antagonistic activities of actinomycetes isolated from Cuc Phuong and Ba Be National Parks against four plant pathogenic fungi
No full textFungal diseases are a huge problem in agriculture, causing serious damage to annual crop yields worldwide. In order to control fungal pathogens in plants, using antagonistic microorganisms is a common approach, especially actinomycetes, as biocontrols considered to be very potential and safe for the environment. With the advantage of high levels of biodiversity, Vietnamese actinomycetes are of a valuable resource for finding strains that are capable of biocontrolling fungal pathogens in plants. Thus, in this study, 70 actinomycete strains were isolated from Cuc Phuong and Ba Be National Parks by four different isolation methods including rehydration centrifugation, sodium dodecyl sulfate – yeast extract, dry heating and dilution methods. Of these, 29 strains (41.4%) belong to rare actinomycete genera including Actinoplanes, Acrocarpospora, Dactylosporangium, Kineosporia, Micromonospora, Nocardia, Nocardiopsis and Pseudonocardia, which are rarely studied in Vietnam. Subsequently, 70 actinomycete strains were subjected to antagonistic activity assays against four highly pathogenic fungi in plants including Alternaria sp., Botrytis cinerea, Colletotrichum gloeosporioides and Phytophthora capsici. The results showed that 80.5% of Streptomyces and 31% of rare actinomyces could inhibit the growth of at least one of the four pathogenic fungal strains. Moreover, ten actinmomycete strains were found to be able to inhibit three types of tested fungal pathogens, simutaneously. Especially, four actinomycete strains (VTCC-A-828, VTCC-A-671, VTCC-A-605, and VTCC-A-69), having the highest antagonistic activity against four fungal pathogens Alternaria sp., Botrytis cinerea, Colletotrichum gloeosporioides and Phytophthora capsici, respectively, were selected. The results in this study indicate the great potential application for Vietnam's microorganisms in the field of plant protection
Isolation and screening producing growth regulator cyanobacteria strains
No full textCyanobacteria are photosynthetic microorganisms that have their biosynthesis capacities for secondary compounds with the high application value. They can produce a variety of bioactive compounds such as lipopeptides, fatty acids, toxins, carotenoids, vitamins and plant growth regulators which could be released into the culture medium. The present study aimed to isolate and screen cyanobacteria strains that could synthesize phytohormone, indole-3-acetic acid (IAA) from paddy soild and fresh water ecosystems (canals, river). Soil and water samples were collected from diferent provinces (Bac Giang, Thanh Hoa and Hue). Indole-3-acetic acid was extracted from the culture of isolated cyanobacteria strains and identified using the Salkowski method. As a result, total 10 strains belonging to 4 genera including Nostoc, Anabena, Geitlerinema and Planktothricoides were susscessful isolated from river, canal and rice field. The morphology of isolated taxa was characterized and monoalgal cultures were grown in BG 11 medium. In L-tryptophan-enriched growth media, all cyanobacteria strains in this research were able to biosynthesize growth regulators with IAA concentrations ranging from 9.1 to 95 µg/mL. Among the isolated cyanobacteria strains, the Planktothricoides raciborskii showed potential for the production of IAA even in the absence of tryptophan in the culture medium. Research results of the L-tryptophan concentration effect on the ability of IAA biosynthesis of this cyanobacteria strain showed that IAA concentration increased gradually and reached the highest value (118,28 ± 2,00 µg/mL) when supplementing L- tryptophan in culture medium at 900 µg/mL. The capacity of producing IAA makes these isolated cyanobacteria an appopriate cadidate for agricultural biotechnology
Structure of insulin-like growth factor 2 (IGF2) gene from striped catfish (Pangasianodon hypophthalmus)
No full textGene coding Insulin-like growth factor 2 (IGF2) is one of genes relating the growth of many fish species, including striped catfish. In this study, cDNA coding to protein IGF2 was isolated from total RNA extracted from liver tissue of catfish, then was amplified through reverse transcription PCR and standard PCR with IGF2 specific primer pair to generate the 642bp-in-size PCR product. The sequence of this cDNA-IGF2 is similar up to 95% to the cDNA-IGF2 gene sequence of catfish included in family Ictalurus. Based on that sequence, 3 primer pairs were designed to amplify 3 regions of IGF2 gene from genomic DNA extracted from fins of catfish, which have 900bp, 1500bp and 1200bp in length. That 3 regions were sequenced and assembled to give the final sequence with 3387bp in length of IGF2 gene, which includes 4 exons coding to IGF2 protein, and is similar up to 96% to sequence of mRNA coding to IGF2 protein of channel catfish Ictalurus punctatus and that of blue catfish Ictalurus furcatus. Determining the structure of IGF2 gene of striped catfish Pangasianodon hypophthalmus enable us to further examine its function and genetic variation
Somatic embryogenesis of Polyscias fruticosa L. Harms via culturing ex vitro leaf explant
No full textPolyscisa fruticosa L. Harms is a medicinal plant containing alkaloids, glycosides, saponins, vitamins and phytosterols with many ginseng-like pharmacological effects such as strengthening fitness, increasing resistance and flexibility. However, the research on micropropagation on this plant is still limited. In this study, post-sterile leaf explants were used as initial culture material for the embryogenic- calli capable of producing somatic embryos (including morphology of somatic embryonic development stages), rooting and evaluation of acclimatization and growth at the greenhouse. The results showed that calli 0.5 cm gave optimum somatic embryos rate (75.53%) on MS medium supplemented with 100 mL/L of coconut water and 0.5 mg/L BA after 6 weeks of culture. The somatic embryo culture on MS medium added 0.1 mg/L Ki combined with 150 mL/L coconut water gave higher shoots regeneration rate (83.30%) and the number of shoots (6.30 shoots) than those cultured on other treatments after 8 weeks of culture. Besides, the in vitro plants were cultured on MS medium supplemented with 30 g/L sucrose and 100 mL/L coconut water for the highest number of roots (3.02 roots) and the ability to tame in the greenhouse (30 soil + 20 vermicomposts + 30 coconut husk + 20 husk ash) for high survival rate of 85.20%
CHARACTERISTICS OF PLASMA ELECTROLYTIC OXIDATION COATINGS ON 6061 AL ALLOY PREPARED AT DIFFERENT CURRENT DENSITIES
No full textPlasma electrolytic oxidation (PEO) has earned much attention due to its powerful and easy formation of hard and corrosion-resistant oxide layers on valve metals, such as Al alloys. Here we report the effects of current density (CD) on microstructure and properties of coatings on 6061 Al alloy by PEO using direct current mode. The electrolyte contains the chemicals of Na2SiO3, Na2WO4´2H2O, and NaH2PO2´H2O. The CDs adopted 5.0, 7.5, 10.0, and 12.5 A/dm2, respectively, for a fixed PEO time of 30 min. The thickness, surface morphology, phase composition, hardness, and corrosion resistance of PEO coatings as the function of the applied CD have been studied and discussed. Studied results show the coating thickness is proportional to the applied CD. When the applied CD increases 2.5 times from 5.0 to 12.5 A/dm2, the growth rate of oxide layers increased by more than 3.5 times, from 0.423 to 1.493 μm/min, respectively. SEM images are characterized by a reduction in the ratio of agglomerate-bumps-region/flatten-region as applied CD increases. However, cracks and larger pores appear when the applied CD is higher than 10.0 A/dm2. X-ray diffraction pattern shows that the main phases of Al, g-Al2O3, α-Al2O3, and W are contained in all coatings. PEO coated sample has the highest hardness of 1290 HV and highest polarization resistance of 8.80 ´ 106 Wcm2 obtained at applied CD 10 A/dm2 which shows the best performance of the coating. The variation in coating performance is explained by microstructure details, specifically phases, compositions of oxide-layers, and micro-pores and cracks
Petrographic and geochemical characteristics of the Nui Chua pegmatoid mafic-ultramafic series, Northern Vietnam: Significance in petrogenesis and Fe-Ti-V metallogenesis
No full textThe pegmatoid intrusions of the Nui Chua complex are one of the important mafic-ultramafic intrusive series associated with Fe-Ti-V ores in northern Vietnam. These intrusions consist of plagiowebsterite, clinopyroxenite, melanogabbronorite, mesogabbro, gabbronorite, and leucogabbronorite. The Fe-Ti oxide ores being massive or disseminated appear layered or veined in pegmatoid rocks. The geochemical characteristics of pegmatoid rocks are rich in Fe, Ti, V and poor Mg; their HREE are higher than LREE, with [La/Yb]N of 0.49 to 0.91 (average: 0.67), showing negative anomalies at Nb, Ta, Th, U, Sr, Zr and positive anomalies at Cs, Ti, and K. The chemical composition and distribution characteristics of trace and rare earth elements of mafic and ultramafic rocks show that they share the same magma source. Having the same geochemical tendency of intrusive formations, Fe-Ti oxide ores are magmatic origin associated with intrusive pegmatoid rocks. The pegmatoid rocks of the Nui Chua complex and Fe-Ti oxide ores are formed as a product of the fractional crystallization of Fe-Ti-rich residual melts after crystallization of the layered rocks
Numerical Analysis of the Characteristics of Glass Photonic Crystal Fibers Infiltrated with Alcoholic Liquids
No full textThe characteristics of PCF with various air hole diameters infiltrated with alcoholic liquids such as ethanol, methanol, propanol and butanol are numerically investigated. Based on the numerical results, we have analyzed and compare in detail the characteristics of these fibers including effective refractive index, effective mode area, dispersion and confinement loss for two case: the diameters and lattices constant of air holes are equal 1 µm and 5µm, 1.42µm and 3.26µm, respectively. The PCF infiltrated with ethanol and butanol showed better near zero flattened dispersion property at 1.42µm and 1µm wavelength respectively. With diameters and lattices constant of air holes equal 1.42μm and 3.26μm, the smallest dispersion of PCF filled with ethanol of 5.91075308 (ps.(nm.km)-1) and methanol of 19.3592474 (ps.(nm.km)-1). The highest ZDW of the PCF infiltrated with ethanol and methanol is 1.24604224µm and 1.22405714µm, respectively. Specially, the value of effective refractive index, effective mode area, dispersion and confinement loss decrease in an orderly manner from butanol, propanol, ethanol to methanol and all the alcoholic liquids’s cuvers of dispersion are flat and are very close to each other and near the zero dispersion curve in case the diameters and lattices constant of air holes are equal 1µm and 5µm. The proposed PCF shows a promising prospect in technology applications such as supercontinuum generation
