Displaying publications 21 - 40 of 43 in total

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  1. Comparison on the cell abundance of Benthic Dinoflagellates in macrophytes and water column collected from open coastal waters and semi-enclosed lagoon
    Normawaty Mohammad-Noor, Asilah Al-Has, Aung T, Shahbudin Saad
    Sains Malaysiana, 2016;45:595-599.
    Benthic dinoflagellates are known to occur in the water column. The reason they can be found in different parts of the ecosystem is not clear. This study aims to determine the species and the cell abundance of benthic dinoflagellates in the water column and macrophytes collected from two different locations i.e. semi-enclosed lagoon and open coastal waters. The physico-chemical parameters (temperature, salinity, pH, dissolved oxygen) and nutrients (nitrate and phosphate) were determined. Results showed that in the lagoon, the most abundant dinoflagellate species on the macrophytes was also the most abundant dinoflagellate species in the water column. The species that dominated the water column and marophytes in the lagoon was Bysmatrum caponii. In the coastal area the trend was not clear. Coolia dominated the macrophytes whereas Peridinium quinquecorne dominated the water column. The physico-chemical parameters determined were similar at both sites except for nutrients. Results show that type of substrates and different geomorphology effects benthic dinoflagellates cell abundance in the macrophytes and water column.
    Matched MeSH terms: Dinoflagellida
  2. Fulltext The genetic intractability of Symbiodinium microadriaticum to standard algal transformation methods
    Chen JE, Barbrook AC, Cui G, Howe CJ, Aranda M
    PLoS One, 2019;14(2):e0211936.
    PMID: 30779749 DOI: 10.1371/journal.pone.0211936
    Modern transformation and genome editing techniques have shown great success across a broad variety of organisms. However, no study of successfully applied genome editing has been reported in a dinoflagellate despite the first genetic transformation of Symbiodinium being published about 20 years ago. Using an array of different available transformation techniques, we attempted to transform Symbiodinium microadriaticum (CCMP2467), a dinoflagellate symbiont of reef-building corals, with the view to performing subsequent CRISPR-Cas9 mediated genome editing. Plasmid vectors designed for nuclear transformation containing the chloramphenicol resistance gene under the control of the CaMV p35S promoter as well as several putative endogenous promoters were used to test a variety of transformation techniques including biolistics, electroporation and agitation with silicon carbide whiskers. Chloroplast-targeted transformation was attempted using an engineered Symbiodinium chloroplast minicircle encoding a modified PsbA protein expected to confer atrazine resistance. We report that we have been unable to confer chloramphenicol or atrazine resistance on Symbiodinium microadriaticum strain CCMP2467.
    Matched MeSH terms: Dinoflagellida/genetics*; Dinoflagellida/metabolism
  3. Salinity effect on growth and toxin production of four tropical Alexandrium species (Dinophyceae)
    Lim PT, Ogata T
    Toxicon, 2005 May;45(6):699-710.
    PMID: 15804519
    Four tropical PSP toxins-producing dinoflagellates, Alexandrium minutum, Alexandrium tamiyavanichii, Alexandrium tamarense and Alexandrium peruvianum from Malaysian waters were studied to investigate the influences of salinity on growth and toxin production. Experiments were conducted on constant temperature 25 degrees C, 140 microE mol m(-2) s(-1) and under 14:10 light:dark photo-cycle with salinity ranged from 2 to 30 psu. The PSP-toxin congeners, GTX 1-6, STX, dcSTX, NEO and C1-C2 were analysed by high performance liquid chromatography. Salinity tolerance of the four species in decreasing order is A. minutum>A. peruvianum>A. tamarense>A. tamiyavanichii. Specific growth rates and maximum densities varied among these species with A. minutum recorded as the highest, 0.5 day(-1) and 6 x 10(4) cells L(-1). Toxin content decreased with elevated salinities in A. minutum, the highest toxin content was about 12 fmole cell(-1) at 5 psu. In A. tamiyavanichii, toxin content peaked at optimal growth salinity (20 and 25 psu). Toxin content of A. tamarense, somehow peaked at sub-optimal growth salinity (15 and 30 psu). Results of this study implied that salinity fluctuation not only influenced the growth physiology but also toxin production of these species.
    Matched MeSH terms: Dinoflagellida/growth & development*; Dinoflagellida/metabolism*
  4. Physiological and transcriptional responses to inorganic nutrition in a tropical Pacific strain of Alexandrium minutum: Implications for the saxitoxin genes and toxin production
    Hii KS, Lim PT, Kon NF, Takata Y, Usup G, Leaw CP
    Harmful Algae, 2016 06;56:9-21.
    PMID: 28073499 DOI: 10.1016/j.hal.2016.04.005
    Saxitoxins (STXs) constitute a family of potent sodium channel blocking toxins, causative agents of paralytic shellfish poisoning (PSP), and are produced by several species of marine dinoflagellates and cyanobacteria. Two STX-core genes, sxtA and sxtG, have been well elucidated in Alexandrium but the expression of these genes under various nutritional modes in tropical species remains unclear. This study investigates the physiological responses of a tropical Pacific strain of Alexandrium minutum growing with nitrate or ammonium, and with various nitrogen to phosphorus (N:P) supply ratios. The transcriptional responses of the sxt genes were observed. Likewise, a putative sxtI encoding O-carbamoyltransferase (herein designated as AmsxtI) was recovered from the transcriptomic data, and its expression was investigated. The results revealed that the cellular toxin quota (Qt) was higher in P-depleted, nitrate-grown cultures. With cultures at similar N:P (<16), cells grown with excess ammonium showed a higher Qt than those grown with nitrate. sxtA1 was not expressed under any culture conditions, suggesting that this gene might not be involved in STX biosynthesis by this strain. Conversely, sxtA4 and sxtG showed positive correlations with Qt, and were up-regulated in P-depleted, nitrate-grown cultures and with excess ambient ammonium. On the other hand, AmsxtI was expressed only when induced by P-depletion, suggesting that this gene may play an important role in P-recycling metabolism, while simultaneously enhancing toxin production.
    Matched MeSH terms: Dinoflagellida/genetics; Dinoflagellida/physiology*
  5. Transcriptional and physiological responses to inorganic nutrition in a tropical Pacific strain of Alexandrium minutum: Implications for nutrient uptakes and assimilation
    Hii KS, Lim PT, Kon NF, Usup G, Gu H, Leaw CP
    Gene, 2019 Aug 30;711:143950.
    PMID: 31255736 DOI: 10.1016/j.gene.2019.143950
    The marine dinoflagellate Alexandrium minutum is known to produce saxitoxins that cause paralytic shellfish poisoning in human worldwide through consumption of the contaminated shellfish mollusks. Despite numerous studies on the growth physiology and saxitoxin production of this species, the knowledge on the molecular basis of nutrient uptakes in relation to toxin production in this species is limited. In this study, relative expressions of the high-affinity transporter genes of nitrate, ammonium, and phosphate (AmNrt2, AmAmt1 and AmPiPT1) and the assimilation genes, nitrate reductase (AmNas), glutamine synthase (AmGSIII) and carbamoyl phosphate synthase (AmCPSII) from A. minutum were studied in batch clonal culture condition with two nitrogen sources (nitrate: NO3- or ammonium: NH4+) under different N:P ratios (high-P: N:P of 14 and 16, and low-P: N:P of 155). The expression of AmAmt1 was suppressed in excess NH4+-grown condition but was not observed in AmNrt2 and AmNas. Expressions of AmAmt1, AmNrt2, AmNas, AmGSIII, AmCPSII, and AmPiPT1 were high in P-deficient condition, showing that A. minutum is likely to take up nutrients for growth under P-stress condition. Conversely, relative expression of AmCPSII was incongruent with cell growth, but was well correlated with toxin quota, suggesting that the gene might involve in arginine metabolism and related toxin production pathway. The expression of AmGSIII is found coincided with higher toxin production and is believed to involve in mechanism to detoxify the cells from excess ammonium stress. The gene regulation observed in this study has provided better insights into the ecophysiology of A. minutum in relation to its adaptive strategies in unfavorable environments.
    Matched MeSH terms: Dinoflagellida/growth & development*; Dinoflagellida/metabolism
  6. Fulltext Biosynthesis of Saxitoxin in Marine Dinoflagellates: An Omics Perspective
    Akbar MA, Mohd Yusof NY, Tahir NI, Ahmad A, Usup G, Sahrani FK, et al.
    Mar Drugs, 2020 Feb 05;18(2).
    PMID: 32033403 DOI: 10.3390/md18020103
    Saxitoxin is an alkaloid neurotoxin originally isolated from the clam Saxidomus giganteus in 1957. This group of neurotoxins is produced by several species of freshwater cyanobacteria and marine dinoflagellates. The saxitoxin biosynthesis pathway was described for the first time in the 1980s and, since then, it was studied in more than seven cyanobacterial genera, comprising 26 genes that form a cluster ranging from 25.7 kb to 35 kb in sequence length. Due to the complexity of the genomic landscape, saxitoxin biosynthesis in dinoflagellates remains unknown. In order to reveal and understand the dynamics of the activity in such impressive unicellular organisms with a complex genome, a strategy that can carefully engage them in a systems view is necessary. Advances in omics technology (the collective tools of biological sciences) facilitated high-throughput studies of the genome, transcriptome, proteome, and metabolome of dinoflagellates. The omics approach was utilized to address saxitoxin-producing dinoflagellates in response to environmental stresses to improve understanding of dinoflagellates gene-environment interactions. Therefore, in this review, the progress in understanding dinoflagellate saxitoxin biosynthesis using an omics approach is emphasized. Further potential applications of metabolomics and genomics to unravel novel insights into saxitoxin biosynthesis in dinoflagellates are also reviewed.
    Matched MeSH terms: Dinoflagellida/genetics*; Dinoflagellida/metabolism*
  7. Phylogenetic relationships, morphological variation, and toxin patterns in the Alexandrium ostenfeldii (Dinophyceae) complex: implications for species boundaries and identities
    Kremp A, Tahvanainen P, Litaker W, Krock B, Suikkanen S, Leaw CP, et al.
    J Phycol, 2014 Feb;50(1):81-100.
    PMID: 26988010 DOI: 10.1111/jpy.12134
    Alexandrium ostenfeldii (Paulsen) Balech and Tangen and A. peruvianum (Balech and B.R. Mendiola) Balech and Tangen are morphologically closely related dinoflagellates known to produce potent neurotoxins. Together with Gonyaulax dimorpha Biecheler, they constitute the A. ostenfeldii species complex. Due to the subtle differences in the morphological characters used to differentiate these species, unambiguous species identification has proven problematic. To better understand the species boundaries within the A. ostenfeldii complex we compared rDNA data, morphometric characters and toxin profiles of multiple cultured isolates from different geographic regions. Phylogenetic analysis of rDNA sequences from cultures characterized as A. ostenfeldii or A. peruvianum formed a monophyletic clade consisting of six distinct groups. Each group examined contained strains morphologically identified as either A. ostenfeldii or A. peruvianum. Though key morphological characters were generally found to be highly variable and not consistently distributed, selected plate features and toxin profiles differed significantly among phylogenetic clusters. Additional sequence analyses revealed a lack of compensatory base changes in ITS2 rRNA structure, low to intermediate ITS/5.8S uncorrected genetic distances, and evidence of reticulation. Together these data (criteria currently used for species delineation in dinoflagellates) imply that the A. ostenfeldii complex should be regarded a single genetically structured species until more material and alternative criteria for species delimitation are available. Consequently, we propose that A. peruvianum is a heterotypic synonym of A. ostenfeldii and this taxon name should be discontinued.
    Matched MeSH terms: Dinoflagellida
  8. Autecology and phylogeny of Coolia tropicalis and Coolia malayensis (Dinophyceae), with emphasis on taxonomy of C. tropicalis based on light microscopy, scanning electron microscopy and LSU rDNA(1)
    Mohammad-Noor N, Moestrup Ø, Lundholm N, Fraga S, Adam A, Holmes MJ, et al.
    J Phycol, 2013 Jun;49(3):536-45.
    PMID: 27007042 DOI: 10.1111/jpy.12062
    Coolia is a widespread and ecologically important genus of benthic marine dinoflagellates found in tropical regions. Historically, there has been taxonomic confusion about the taxonomy and toxicity of this group. The goal of this study was to resolve morphological questions concerning Coolia tropicalis and determine the taxonomic identity of the Australian Coolia isolate which has been reported to produce cooliatoxins. To accomplish this, the morphology of tropical strains from Belize (the type locality of C. tropicalis), Malaysia, Indonesia, and Australia were examined and compared to published reports. The morphological analysis showed that C. tropicalis differs from the original description in that it has a slightly larger size (35-47 μm long by 30-45 μm wide versus 23-40 μm long by 25-39 μm wide), and the shape of fourth apical plate, and the length of Po plate (7.4-12 μm versus 7 μm). Based on both morphology and phylogenetic analysis using LSU D1- D3 rDNA sequences, the clones of C. tropicalis from Malaysia, Indonesia, and Belize were found to form a monophyletic clade within the genus. The strain producing cooliatoxin was found to be C. tropicalis, not Coolia monotis as originally assumed. To explore the factors influencing the growth of Coolia species, the growth rates of C. tropicalis and Coolia malayensis were determined at different temperatures and salinities. Both species tolerated a wide range of temperatures, but cannot survive at temperatures <20°C or >35°C. C. monotis, the dominant species reported in the literature, probably does not produce toxins.
    Matched MeSH terms: Dinoflagellida
  9. Microplankton bloom in a brackish water lagoon of Terengganu
    Shamsudin L, Shazili NA
    Environ Monit Assess, 1991 Oct;19(1-3):287-94.
    PMID: 24233946 DOI: 10.1007/BF00401318
    Increased primary plankton productivity was observed in a brackish water lagoon of Terengganu during the study period between January 1988 to December 1988. The lagoon is also the site for the fish cage culture activities of sea bass during the study period. An examination of water quality at the sampling stations during the study period indicated that both the organic and inorganic nutrients were high during the pre-monsoon period. The source of the nutrient in the lagoon was believed to be derived from the agro-based industrial effluents, fertilisers from paddy fields as well as untreated human and animal wastes. This coincided with the peak production of plankton in the surface waters of the brackish water lagoon. During this period both cultured and indigenous fish species were seen to suffer from oxygen asphyxiation (suffocation due to lack of oxygen). The primary productivity values ranged from 9 to 22 μg/L/h during the peak period while the microplankton species were composed of diatom, flagellates and dinoflagellates. Reduction in the primary productivity values were obtained with reduction in sallinity, specially during the peak monsoon months (November to March) corresponding to the Northeast monsoon period.
    Matched MeSH terms: Dinoflagellida
  10. Fulltext Effects of substratum and depth on benthic harmful dinoflagellate assemblages
    Lee LK, Lim ZF, Gu H, Chan LL, Litaker RW, Tester PA, et al.
    Sci Rep, 2020 07 09;10(1):11251.
    PMID: 32647125 DOI: 10.1038/s41598-020-68136-6
    Microhabitats influence the distribution and abundance of benthic harmful dinoflagellate (BHAB) species. Currently, much of the information on the relationships between BHABs and microhabitat preferences is based on non-quantitative anecdotal observations, many of which are contradictory. The goal of this study was to better quantify BHAB and microhabitat relationships using a statistically rigorous approach. Between April 2016 to May 2017, a total of 243 artificial substrate samplers were deployed at five locations in the Perhentian Islands, Malaysia while simultaneous photo-quadrat surveys were performed to characterize the benthic substrates present at each sampling site. The screen samplers were retrieved 24 h later and the abundances of five BHAB genera, Gambierdiscus, Ostreopsis, Coolia, Amphidinium, and Prorocentrum were determined. Substrate data were then analyzed using a Bray-Curtis dissimilarity matrix to statistically identify distinct microhabitat types. Although BHABs were associated with a variety of biotic and abiotic substrates, the results of this study demonstrated differing degrees of microhabitat preference. Analysis of the survey results using canonical correspondence analysis explained 70.5% (horizontal first axis) and 21.6% (vertical second axis) of the constrained variation in the distribution of various genera among microhabitat types. Prorocentrum and Coolia appear to have the greatest range being broadly distributed among a wide variety of microhabitats. Amphidinium was always found in low abundances and was widely distributed among microhabitats dominated by hard coral, turf algae, sand and silt, and fleshy algae and reached the highest abundances there. Gambierdiscus and Ostreopsis had more restricted distributions. Gambierdiscus were found preferentially associated with turf algae, hard coral and, to a lesser extent, fleshy macroalgae microhabitats. Ostreopsis, almost always more abundant than Gambierdiscus, preferred the same microhabitats as Gambierdiscus and were found in microbial mats as well. With similar habitat preferences Ostreopsis may serve as an indicator organism for the presence of Gambierdiscus. This study provides insight into how BHAB-specific microhabitat preferences can affect toxicity risks.
    Matched MeSH terms: Dinoflagellida
  11. Fulltext Development of species-specific molecular marker for Pyrodinium bahamense var. compressum (Gonyaulacales, Dinophyceae) based on 18S ribosomal DNA sequence
    CHIN, W. L., ANTON, A., KUMAR, S.V., TEOH, P. L.
    Buletin Persatuan Genetik Malaysia, 2010;17(1):5-8.
    MyJurnal
    In Malaysia, harmful algal blooms often occur along the coastal waters of west Sabah, where one of the causative organisms is the toxin-producing dinoflagellate, Pyrodinium bahamense var. compressum. A total of five P. bahamense var. compressum isolates were obtained from four locations and were cultured in f/2 medium. A Polymerase Chain Reaction (PCR) based technique was developed and used to screen for the presence of the dinoflagellate, P. bahamense var. compressum. A dinoflagellate-specific primer pair was designed based on sequences of P. bahamense var. compressum to amplify the 18S small subunit ribosomal DNA (rDNA) sequences. The rDNA of the P. bahamense var. compressum isolates were obtained. A species-specific primer pair was designed to target a 600 bp rDNA sequence of the target dinoflagellate. The primer pair targeting P. bahamense var. compressum did not yield any product with the fifteen algae cultures used as negative controls, but only amplified the rDNA of P. bahamense var. compressum cultures. The PCR method for identification of P. bahamense var. compressum was also applied on twenty field samples collected with plankton net. P. bahamense var. compressum cells were detected by PCR in five field samples and were confirmed by direct sequencing. From this study, a species-specific primer pair was obtained to identify the target species, P. bahamense var. compressum, among the natural complex communities of seawater.
    Matched MeSH terms: Dinoflagellida
  12. New scenario for speciation in the benthic dinoflagellate genus Coolia (Dinophyceae)
    Leaw CP, Tan TH, Lim HC, Teng ST, Yong HL, Smith KF, et al.
    Harmful Algae, 2016 05;55:137-149.
    PMID: 28073527 DOI: 10.1016/j.hal.2016.02.010
    In this study, inter- and intraspecific genetic diversity within the marine harmful dinoflagellate genus Coolia Meunier was evaluated using isolates obtained from the tropics to subtropics in both Pacific and Atlantic Ocean basins. The aim was to assess the phylogeographic history of the genus and to clarify the validity of established species including Coolia malayensis. Phylogenetic analysis of the D1-D2 LSU rDNA sequences identified six major lineages (L1-L6) corresponding to the morphospecies Coolia malayensis (L1), C. monotis (L2), C. santacroce (L3), C. palmyrensis (L4), C. tropicalis (L5), and C. canariensis (L6). A median joining network (MJN) of C. malayensis ITS2 rDNA sequences revealed a total of 16 haplotypes; however, no spatial genetic differentiation among populations was observed. These MJN results in conjunction with CBC analysis, rDNA phylogenies and geographical distribution analyses confirm C. malayensis as a distinct species which is globally distributed in the tropical to warm-temperate regions. A molecular clock analysis using ITS2 rDNA revealed the evolutionary history of Coolia dated back to the Mesozoic, and supports the hypothesis that historical vicariant events in the early Cenozoic drove the allopatric differentiation of C. malayensis and C. monotis.
    Matched MeSH terms: Dinoflagellida
  13. Fulltext Genome Sequence of Bacillus sp. Strain UMTAT18 Isolated from the Dinoflagellate Alexandrium tamiyavanichii Found in the Straits of Malacca
    Danish-Daniel M, Ming GH, Mohd Noor ME, Sung YY, Usup G
    Genome Announc, 2016 Oct 6;4(5).
    PMID: 27795265 DOI: 10.1128/genomeA.01106-16
    Bacillus sp. strain UMTAT18 was isolated from the harmful dinoflagellate Alexandrium tamiyavanichii Its genome consists of 5,479,367 bp with 5,546 open reading frames, 102 tRNAs, and 29 rRNAs. Gene clusters for biosynthesis of nonribosomal peptides, bacteriocin, and lantipeptide were identified. It also contains siderophore and genes related to stress tolerance.
    Matched MeSH terms: Dinoflagellida
  14. Harmful algal blooms in Malaysian waters
    Lim PT, Usup Gires, Leaw CP
    Sains Malaysiana, 2012;41:1509-1515.
    Harmful algal blooms (HABs) events have been increasingly reported in the country, not only of the frequency and severity of the events, but also involved more species than previously known. In this paper, a decadal review of HABs events in Malaysia is summarized. Bloom events caused by harmful dinoflagellate species including the shellfish poisoning events were highlighted. Paralytic shellfish poisoning (PSP) is no longer restricted to Sabah coasts and Pyrodnium bahamense. Bloom of Alexandrium minutum was reported for the first time in the Peninsula with six persons hospitalized including one casualty after consuming the contaminated benthic clams. Algal blooms that are associated with incidence of massive fish kills have been reported from both east and west coasts of the Peninsula in conjunction to finfish mariculture loses. The culprits of these bloom events have been identified as the dinoflagellates, Cochlodinium polykrikoides, Neoceratium furca, Prorocentrum minimum, Noctiluca scintillans and a raphidophyte, Chatonella ovata. In this paper, some of these HABs species were characterized morphologically and genetically, including their toxicity. Therefore, with the increase of coastal utilization and eutrophication, prevention, management and mitigation strategies, such as site selection, moving pens, clay spraying should be adopted to minimize the impact of these natural events.
    Matched MeSH terms: Dinoflagellida
  15. An evaluation of the genus Amphidinium (Dinophyceae) combining evidence from morphology, phylogenetics, and toxin production, with the introduction of six novel species
    Karafas S, Teng ST, Leaw CP, Alves-de-Souza C
    Harmful Algae, 2017 09;68:128-151.
    PMID: 28962975 DOI: 10.1016/j.hal.2017.08.001
    The genus Amphidinium is an important group of athecated dinoflagellates because of its high abundance in marine habitats, its member's ability to live in a variety of environmental conditions and ability to produce toxins. Furthermore, the genus is of particular interest in the biotechnology field for its potential in the pharmaceutical arena. Taxonomically the there is a history of complication and confusion over the proper identities and placements of Amphidinium species due to high genetic variability coupled with high morphological conservation. Thirteen years has passed since the most recent review of the group, and while many issues were resolved, some remain. The present study used microscopy, phylogenetics of the 28S region of rDNA, secondary structure of the ITS2 region of rDNA, compensatory base change data, and cytotoxicity data from Amphidinium strains collected world-wide to elucidate remaining confusion. This holistic approach using multiple lines of evidence resulted in a more comprehensive understanding of the morphological, ecological, and genetic characteristics that are attributed to organisms belonging to Amphidinium, including six novel species: A. fijiensis, A. magnum, A. paucianulatum, A. pseudomassartii, A. theodori, and A. tomasii.
    Matched MeSH terms: Dinoflagellida/classification*; Dinoflagellida/cytology*; Dinoflagellida/ultrastructure
  16. Analysis of paralytic shellfish poisoning toxin congeners by a sodium channel receptor binding assay
    Usup G, Leaw CP, Cheah MY, Ahmad A, Ng BK
    Toxicon, 2004 Jul;44(1):37-43.
    PMID: 15225560
    This study was carried out to characterize the detection and quantitation of several paralytic shellfish poisoning (PSP) toxin congeners using a receptor binding assay (RBA). This involved competitive binding of the toxin congeners against tritium-labeled STX for receptor sites on rat brain sodium channels. Competitive binding curves were described by a four-parameter logistic equation. Half-saturation values (EC(50)) ranged from 4.38 nM for STX to 142 nM for GTX5. Receptor binding affinity was in the order STX>GTX1/4>neoSTX>GTX2/3>dcSTX>GTX5, and this was similar to the order of mouse toxicity of these congeners. Predicted toxin concentrations from observed STXeq values and EC(50) ratios relative to STX were within 20% or better of the actual concentrations used in the assay. In contrast predicted toxin concentrations using mouse toxicity ratios relative to STX did not provide a good match to actual concentrations, except for GTX1/4. This study has shown that the rat brain sodium channel RBA will provide a reliable integration of total toxicity of various PSP toxin congeners present in a sample.
    Matched MeSH terms: Dinoflagellida/chemistry*
  17. Fulltext Loktanella spp. Gb03 as an algicidal bacterium, isolated from the culture of Dinoflagellate Gambierdiscus belizeanus
    Bloh AH, Usup G, Ahmad A
    Vet World, 2016 Feb;9(2):142-6.
    PMID: 27051199 DOI: 10.14202/vetworld.2016.142-146
    AIM: Bacteria associated with harmful algal blooms can play a crucial role in regulating algal blooms in the environment. This study aimed at isolating and identifying algicidal bacteria in Dinoflagellate culture and to determine the optimum growth requirement of the algicidal bacteria, Loktanella sp. Gb-03.

    MATERIALS AND METHODS: The Dinoflagellate culture used in this study was supplied by Professor Gires Usup's Laboratory, School of Environmental and Natural Resources Sciences, Faculty of Science and Technology, University Kebangsaan Malaysia, Malaysia. The culture was used for the isolation of Loktanella sp., using biochemical tests, API 20 ONE kits. The fatty acid content of the isolates and the algicidal activity were further evaluated, and the phenotype was determined through the phylogenetic tree.

    RESULTS: Gram-negative, non-motile, non-spore-forming, short rod-shaped, aerobic bacteria (Gb01, Gb02, Gb03, Gb04, Gb05, and Gb06) were isolated from the Dinoflagellate culture. The colonies were pink in color, convex with a smooth surface and entire edge. The optimum growth temperature for the Loktanella sp. Gb03 isolate was determined to be 30°C, in 1% of NaCl and pH7. Phylogenetic analysis based on 16S rRNA gene sequences showed that the bacterium belonged to the genus Loktanella of the class Alphaproteobacteria and formed a tight cluster with the type strain of Loktanella pyoseonensis (97.0% sequence similarity).

    CONCLUSION: On the basis of phenotypic, phylogenetic data and genetic distinctiveness, strain Gb-03, were placed in the genus Loktanella as the type strain of species. Moreover, it has algicidal activity against seven toxic Dinoflagellate. The algicidal property of the isolated Loktanella is vital, especially where biological control is needed to mitigate algal bloom or targeted Dinoflagellates.

    Matched MeSH terms: Dinoflagellida
  18. Dinoflagellate bloom in tropical fish ponds of coastal waters of the South China Sea
    Shamsudin L, Awang A, Ambak A, Ibrahim S
    Environ Monit Assess, 1996 May;40(3):303-11.
    PMID: 24198160 DOI: 10.1007/BF00398875
    Red tide of dinoflagellate was observed in brackish water fish ponds of Terengganu along the coast of the South China Sea during the study period between January 1992 to December 1992. The nearby coastal moat water facing the South China Sea is the source of water for fish pond culture activities of sea bass during the study period. An examination of water quality in fish ponds during the study period indicated that both the organic nutrients were high during the pre-wet monsoon period. The source of the nutrients in coastal water was believed to be derived from the agro-based industrial effluents, fertilizers from paddy fields and untreated animal wastes. This coincided with the peak production of dinoflagellate in the water column in October 1992. The cell count ranges from 8.3 to 60.4×10.4×10(4)/l during the bloom peak period and the bloom species were compared entirely of non-toxic dinoflagellates with Protoperidinium quinquecorne occurring >90% of the total cell count. However, both cultured and indigenous fish species were seen to suffer from oxygen asphyxiation (suffocation due to lack of oxygen). The bloom lasted for a short period (4-5 days) with a massive cell collapse from subsurface to bottom water on the sixth day. The productivity values ranged from 5-25 C g/ l / h with a subsurface maximum value in October 1992. Two species of Ciliophora, Tintinnopsis and Favella, were observed to graze on these dinoflagellates at the end of the bloom period.
    Matched MeSH terms: Dinoflagellida
  19. Effects of environmental conditions and nutrients on the occurrence and distribution of potentially harmful phytoplankton in mesotrophic water
    Soon TK, Julian Ransangan
    Sains Malaysiana, 2016;45:865-877.
    Marudu Bay, north coast of Sabah is characterized with mesotrophic water body and typical environmental parameters
    throughout the year. The current study was undertaken to evaluate the effect of environmental parameters and nutrients
    in mesotrophic water on the occurrence and distribution of potentially harmful phytoplankton species. The samplings
    were conducted over a period of thirteen months, covering southwest monsoon (SWM), inter-monsoon (IM), and northeast
    monsoon (NEM), at ten stations throughout the bay. Physical parameters (temperature, salinity, pH, dissolved oxygen,
    current speed and secchi depth), biological parameters (cell densities of phytoplankton) and chemical parameters
    (phosphate, nitrate, silicate and ammonia) were examined. The results indicated at least eight potentially harmful
    phytoplankton species (Dinophysis caudata, D. miles, Ceratium furca, C. fursus, Prorocentrum micans, P. sigmoides, P.
    triestinum and Pseudo-nitzschia sp.) were detected in north coast of Sabah. However, the potentially harmful phytoplankton
    species contributed only about 1.3% of the total phytoplankton community. Under nutrient deprivation conditions, the
    potentially harmful phytoplankton species distribution was mainly influenced by the ability to utilize other nitrogen
    sources, cell mobility and toleration to low nutrients environments.
    Matched MeSH terms: Dinoflagellida
  20. Fulltext Resting Cyst Distribution and Molecular Identification of the Harmful Dinoflagellate Margalefidinium polykrikoides (Gymnodiniales, Dinophyceae) in Lampung Bay, Sumatra, Indonesia
    Thoha H, Muawanah, Bayu Intan MD, Rachman A, Sianturi OR, Sidabutar T, et al.
    Front Microbiol, 2019;10:306.
    PMID: 30846977 DOI: 10.3389/fmicb.2019.00306
    Margalefidinium polykrikoides, an unarmored dinoflagellate, was suspected to be the causative agent of the harmful algal blooms - associated with massive fish mortalities - that have occurred continually in Lampung Bay, Indonesia, since the first bloom event in October 2012. In this study, after examination of the morphology of putative M. polykrikoides-like cysts sampled in bottom sediments, cyst bed distribution of this harmful species was explored in the inner bay. Sediment samples showed that resting cysts, including several morphotypes previously reported as M. polykrikoides, were most abundant on the northern coast of Lampung Bay, ranging from 20.6 to 645.6 cysts g-1 dry sediment. Molecular phylogeny inferred from LSU rDNA revealed that the so-called Mediterranean ribotype was detected in the sediment while M. polykrikoides motile cells, four-cell chain forming in bloom conditions, belonged to the American-Malaysian ribotype. Moreover, hyaline cysts, exclusively in the form of four-cell chains, were also recorded. Overall, these results unequivocally show that the species M. polykrikoides is abundantly present, in the form of vegetative cells, hyaline and resting cysts in an Indonesian area.
    Matched MeSH terms: Dinoflagellida
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