Displaying publications 21 - 40 of 50 in total

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  1. Culture of the calanoid copepod, Acartia erythraea and cyclopoid copepod, Oithona brevicornis with various microalgal diets
    Rajkumar M, Mohammad Mustafizur Rahman
    Sains Malaysiana, 2016;45:615-620.
    Two experiments were conducted to develop Acartia erythraea and Oithona brevicornis cultures: The performance of five microalgal diets to produce nauplii, copepodites and adults of A. erythraea; and the performance of the same diets to produce nauplii, copepodites and adults of O. brevicornis. The five different microalgal diets were Isochrysis galbana (IG), Chaetoceros affinis (CA), Chlorella marina (CM), Nannochloropsis oculata (NO) and mixed algae (mixture of IG, CA, CM and NO at an equal abundance to provide the exact cell density). The results indicated that the abundance of both A. erythraea and O. brevicornis was higher in tanks supplied with IG and mixed algae than the tanks supplied with CA, CM and NO. IG and mixed algal diets were statistically similar on the mean abundance for both A. erythraea and O. brevicornis. The maximum production of A. erythraea nauplii was observed on day 12 of culture period and the nauplii production decreased from day 13 onwards. The mean abundance of A. erythraea copepodites and adults increased along with time up to the end of the culture period. In the case of O. brevicornis nauplii, the maximum abundance was observed on day 9 day of culture period and the nauplii production decreased from day 10 onwards. The mean abundance of O. brevicornis copepodites and adults increased gradually from the beginning to the end of the culture period. Under the experimental conditions of this study, both IG and mixed algal diets can be recommended for the best growth performance of A. erythraea and O. brevicornis.
    Matched MeSH terms: Diatoms
  2. Prevalence of diatom frustules in non-vegetarian foodstuffs and its implications in interpreting identification of diatom frustules in drowning cases
    Yen LY, Jayaprakash PT
    Forensic Sci Int, 2007 Jul 20;170(1):1-7.
    PMID: 17023133
    Detection of diatom frustules in bone marrow (diatom test) is used for diagnosing ante-mortem drowning where the usual signs of drowning are not present in dead bodies recovered from water. However, controversies over the reliability of diatom test results are continuing. There have been indications on the possibilities of diatoms entering into systemic circulation from atmospheric air, food and drink. While diatoms have been demonstrated in the gut content of edible marine forms such as shrimps and clams, the present study, for the first time, provides empirical evidence on the prevalence as well as abundance of diatom frustules in the samples of cooked non-vegetarian foodstuffs that impend human consumption in Kelantan, Malaysia. It is found that 50 g each of cleaned and cooked prawns and of clams impending human consumption contain about 8360 and 29,054 diatom frustules, respectively. A person accustomed to prawn and clam food would be ingesting an estimated 2 million diatoms in a single year. Considering the suggestion that detection of five diatom frustules in 10 g of bone marrow would suffice for concluding drowning as mode of death, and the fact that there is yet no proof that diatom frustules do not enter into the human systemic circulation through the digestive tract, the estimated number of diatom frustules routinely ingested acquires significance since entry of a few of such ingested frustules into the systemic circulation can lead to false positive test results. The findings of this research raise two important issues: first, population based routine food related diatom ingestion requires to be estimated, and, second, studies have to be initiated to categorically prove or disprove the possibility of entry of diatom frustules into the systemic circulation via the digestive tract.
    Matched MeSH terms: Diatoms/isolation & purification*; Diatoms/ultrastructure
  3. Fulltext A preliminary study on automated freshwater algae recognition and classification system
    Mosleh MA, Manssor H, Malek S, Milow P, Salleh A
    BMC Bioinformatics, 2012;13 Suppl 17:S25.
    PMID: 23282059 DOI: 10.1186/1471-2105-13-S17-S25
    Freshwater algae can be used as indicators to monitor freshwater ecosystem condition. Algae react quickly and predictably to a broad range of pollutants. Thus they provide early signals of worsening environment. This study was carried out to develop a computer-based image processing technique to automatically detect, recognize, and identify algae genera from the divisions Bacillariophyta, Chlorophyta and Cyanobacteria in Putrajaya Lake. Literature shows that most automated analyses and identification of algae images were limited to only one type of algae. Automated identification system for tropical freshwater algae is even non-existent and this study is partly to fill this gap.
    Matched MeSH terms: Diatoms/classification*; Diatoms/cytology*
  4. First report of the toxigenic Nitzschia navis-varingica (Bacillariophyceae) isolated from Tebrau Straits, Johor, Malaysia
    Suriyanti SN, Usup G
    Toxicon, 2015 Dec 15;108:257-63.
    PMID: 26541573 DOI: 10.1016/j.toxicon.2015.10.017
    Screening of the occurrence of potentially toxic diatoms was carried out at two sites of cage cultures in Tebrau Straits, Johor. Phytoplankton samples from Sungai Pendas and Teluk Sengat were collected using a 20 μm mesh plankton net and salinity was recorded in-situ. Nitzschia and Pseudo-nitzschia cells were isolated and established into clonal cultures. All cultures were tested for domoic acid using HPLC-UV analysis and verified by LC-MS analysis. Three Nitzschia spp. and one Pseudo-nitzschia sp. were identified from these locations. Toxic and non-toxic strains of Nitzschia navis-varingica are found at the cage culture areas. Cellular toxin content in the toxic strain of N. navis-varingica is 1.8 pg cell(-1). This is a new record from Malaysia and this species was isolated from estuarine water with salinity 28 PSU. The discovery of toxic Nitzschia species in Tebrau Straits indicates the potential for domoic acid accumulation in seafood.
    Matched MeSH terms: Diatoms/classification*; Diatoms/isolation & purification
  5. Phylogeny and species delineation in the marine diatom Pseudo-nitzschia (Bacillariophyta) using cox1, LSU, and ITS2 rRNA genes: A perspective in character evolution
    Lim HC, Tan SN, Teng ST, Lundholm N, Orive E, David H, et al.
    J Phycol, 2018 04;54(2):234-248.
    PMID: 29377161 DOI: 10.1111/jpy.12620
    Analyses of the mitochondrial cox1, the nuclear-encoded large subunit (LSU), and the internal transcribed spacer 2 (ITS2) RNA coding region of Pseudo-nitzschia revealed that the P. pseudodelicatissima complex can be phylogenetically grouped into three distinct clades (Groups I-III), while the P. delicatissima complex forms another distinct clade (Group IV) in both the LSU and ITS2 phylogenetic trees. It was elucidated that comprehensive taxon sampling (sampling of sequences), selection of appropriate target genes and outgroup, and alignment strategies influenced the phylogenetic accuracy. Based on the genetic divergence, ITS2 resulted in the most resolved trees, followed by cox1 and LSU. The morphological characters available for Pseudo-nitzschia, although limited in number, were overall in agreement with the phylogenies when mapped onto the ITS2 tree. Information on the presence/absence of a central nodule, number of rows of poroids in each stria, and of sectors dividing the poroids mapped onto the ITS2 tree revealed the evolution of the recently diverged species. The morphologically based species complexes showed evolutionary relevance in agreement with molecular phylogeny inferred from ITS2 sequence-structure data. The data set of the hypervariable region of ITS2 improved the phylogenetic inference compared to the cox1 and LSU data sets. The taxonomic status of P. cuspidata and P. pseudodelicatissima requires further elucidation.
    Matched MeSH terms: Diatoms/classification*; Diatoms/genetics
  6. 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: Diatoms
  7. Strain-related physiological and behavioral effects of Skeletonema marinoi on three common planktonic copepods
    Md Amin R, Koski M, Båmstedt U, Vidoudez C
    Mar Biol, 2011;158(9):1965-1980.
    PMID: 24391269
    Three strains of the chain-forming diatom Skeletonema marinoi, differing in their production of polyunsaturated aldehydes (PUA) and nutritional food components, were used in experiments on feeding, egg production, hatching success, pellet production, and behavior of three common planktonic copepods: Acartia tonsa, Pseudocalanus elongatus, and Temora longicornis. The three different diatom strains (9B, 1G, and 7J) induced widely different effects on Acartia tonsa physiology, and the 9B strain induced different effects for the three copepods. In contrast, different strains induced no or small alterations in the distribution, swimming behavior, and turning frequency of the copepods. 22:6(n-3) fatty acid (DHA) and sterol content of the diet typically showed a positive effect on either egg production (A. tonsa) or hatching success (P. elongatus), while other measured compounds (PUA, other long-chain polyunsaturated fatty acids) of the algae had no obvious effects. Our results demonstrate that differences between strains of a given diatom species can generate effects on copepod physiology, which are as large as those induced by different algae species or groups. This emphasizes the need to identify the specific characteristics of local diatoms together with the interacting effects of different mineral, biochemical, and toxic compounds and their potential implications on different copepod species.
    Matched MeSH terms: Diatoms
  8. Fulltext High Productivity of Eicosapentaenoic Acid and Fucoxanthin by a Marine Diatom Chaetoceros gracilis in a Semi-Continuous Culture
    Tachihana S, Nagao N, Katayama T, Hirahara M, Yusoff FM, Banerjee S, et al.
    Front Bioeng Biotechnol, 2020;8:602721.
    PMID: 33363132 DOI: 10.3389/fbioe.2020.602721
    Significantly high eicosapentaenoic acid (EPA) and fucoxanthin contents with high production rate were achieved in semi continuous culture of marine diatom. Effects of dilution rate on the production of biomass and high value biocompounds such as EPA and fucoxanthin were evaluated in semi-continuous cultures of Chaetoceros gracilis under high light condition. Cellular dry weight increased at lower dilution rate and higher light intensity conditions, and cell size strongly affected EPA and fucoxanthin contents. The smaller microalgae cells showed significantly higher (p < 0.05) value of 17.1 mg g-dw-1 fucoxanthin and 41.5% EPA content per total fatty acid compared to those observed in the larger cells. Chaetoceros gracilis can accumulate relatively higher EPA and fucoxanthin than those reported previously. In addition, maintenance of small cell size by supplying sufficient nutrients and light energy can be the key for the increase production of valuable biocompounds in C. gracilis.
    Matched MeSH terms: Diatoms
  9. Effect of irradiance on the emission of short-lived halocarbons from three common tropical marine microalgae
    Lim YK, Keng FS, Phang SM, Sturges WT, Malin G, Abd Rahman N
    PeerJ, 2019;7:e6758.
    PMID: 31041152 DOI: 10.7717/peerj.6758
    Marine algae have been reported as important sources of biogenic volatile halocarbons that are emitted into the atmosphere. These compounds are linked to destruction of the ozone layer, thus contributing to climate change. There may be mutual interactions between the halocarbon emission and the environment. In this study, the effect of irradiance on the emission of halocarbons from selected microalgae was investigated. Using controlled laboratory experiments, three tropical marine microalgae cultures, Synechococcus sp. UMACC 371 (cyanophyte), Parachlorella sp. UMACC 245 (chlorophyte) and Amphora sp. UMACC 370 (diatom) were exposed to irradiance of 0, 40 and 120 µmol photons m-2s-1. Stress in the microalgal cultures was indicated by the photosynthetic performance (Fv/Fm, maximum quantum yield). An increase in halocarbon emissions was observed at 120 µmol photons m-2s-1, together with a decrease in Fv/Fm. This was most evident in the release of CH3I by Amphora sp. Synechococcus sp. was observed to be the most affected by irradiance as shown by the increase in emissions of most halocarbons except for CHBr3 and CHBr2Cl. High positive correlation between Fv/Fm and halocarbon emission rates was observed in Synechococcus sp. for CH2Br2. No clear trends in correlation could be observed for the other halocarbons in the other two microalgal species. This suggests that other mechanisms like mitochondria respiration may contribute to halocarbon production, in addition to photosynthetic performance.
    Matched MeSH terms: Diatoms
  10. Effect of high temperature toward microalgal organic matter and its impact toward membrane distillation application
    Cheah YT, Lakbir Singh HKK, Chan DJC
    Water Environ Res, 2021 Jan 23.
    PMID: 33484623 DOI: 10.1002/wer.1515
    Membrane distillation (MD) frequently deals with membrane biofouling caused by deposition of algal organic matter (AOM) from algal blooms, hampering the treatment efficiency. In this study, AOMs, which are soluble extracellular polymeric substance (sEPS), bounded EPS (bEPS), and internal organic matter (IOM) from three benthic species (Amphora coffeaeformis, Cylindrotheca fusiformis, and Navicula incerta) were exposed to a temperature range to resemble the MD process. Results showed that EPS had higher polysaccharide fraction than protein with 85.71%, 68.26%, and 71.91% for A. coffeaeformis, N. incerta, and C. fusiformis, respectively. Both the EPS polysaccharide and protein concentration linearly increase with temperature, but the opposite was true for IOM and high-molecular-weight (HMW) polysaccharide. At 80°C, 5812.94 μg/g out of 6304.28 μg/g polysaccharide in A. coffeaeformis was of low molecular weight (LMW); hence, these findings suggested that they were the major foulants to clog the narrow pores within virgin hydrophobic membrane, forming a conditioning layer followed by deposition of HMW and hydrophilic polysaccharides onto the macropores to cause irreversible fouling. Cell lysis occurring at higher temperature increases the total protein content about 25% within the EPS matrix, inducing membrane plugging via hydrophobic-hydrophobic interactions. Overall, the AOM composition at different temperatures will likely dictate the fouling severity in MD. PRACTITIONER POINTS: EPS production of three benthic diatoms was the highest at 80°C. EPS from diatoms consists of at least 75.29% of polysaccharides. Small molecular weight carbohydrates (<12 kDa) were potential foulants. Proteins of internal organic matter (>56%) give irreversible attachment towards membranes. A. coffeaeformis was considered as the most fouling diatoms with highest EPS amount of 6304.28 μg/g.
    Matched MeSH terms: Diatoms
  11. Pseudo-nitzschia nanaoensis sp. nov. (Bacillariophyceae) from the Chinese coast of the South China Sea
    Li Y, Dong HC, Teng ST, Bates SS, Lim PT
    J Phycol, 2018 12;54(6):918-922.
    PMID: 30270437 DOI: 10.1111/jpy.12791
    Pseudo-nitzschia nanaoensis sp. nov. is described from waters around Nan'ao Island (South China Sea), using morphological data and molecular evidence. This species is morphologically most similar to P. brasiliana, but differs by a denser arrangement of fibulae, interstriae, and poroids, as well as by the structure of the valvocopula and the narrow second band. Pseudo-nitzschia nanaoensis constitutes a monophyletic lineage and is well differentiated from other species on the LSU and ITS2 sequence-structure trees. Pseudo-nitzschia nanaoensis makes up the basal node on the LSU tree, and forms a sister clade with a group of P. pungens and P. multiseries on the ITS2 tree. The ability of cultured strains to produce domoic acid was assessed, including its possible induction by the presence of a copepod and brine shrimp, by liquid chromatography-tandem mass spectrometry. However, no strains showed detectable domoic acid.
    Matched MeSH terms: Diatoms
  12. Pure Cultivation and Morphological Studies of Four Chaetoceros Taxa from the Coastal Waters of Pahang, Malaysia
    M.A.M. Fuad, N. Mohammad-Noor, A.K.C. Jalal, B.Y. Kamaruzzaman
    Sains Malaysiana, 2015;44:947-955.
    This study was conducted to study the morphological features of species under the genus Chaetoceros isolated from the coastal waters of Pahang, Malaysia. The species were isolated, cultivated and viewed under light microscope (LM) and scanning electron microscope (SEM). Four taxa were successfully isolated and cultivated in pure culture, namely Chaetoceros affinis var. affinis, Chaetoceros affinis var. willei, Chaetoceros anastomosans and Chaetoceros baculites. Both varieties of C. affinis were considered as distinct taxa where both strains can be distinguished based on morphological characteristics. C. affinis var. affinis has a thick cell wall compared with C. affinis var. willei. C. anastomosans has special features including a silica bar on the intersection of setae and the production of mucous. The length of the aperture opening is a new record from this study. The new record obtained for C. baculites includes the size of the aperture, the terminal setae, spinal arrangement, the thinness of the cell wall and the location of the species in tropical waters. Detailed data on each species will be added to the taxonomic information for future studies.
    Matched MeSH terms: Diatoms
  13. Drowning
    Sarvesvaran R
    Malays J Pathol, 1992 Dec;14(2):77-83.
    PMID: 1304628
    A body recovered from the water does not necessarily imply that death was due to drowning. The diagnosis of drowning is discussed together with the significance of the "diatom" and biochemical tests.
    Matched MeSH terms: Diatoms*
  14. Toxicity of produced water from crude oil terminals to Photobacterium phosphoreum, Chaetoceros sp., and Donax faba
    Din ZB, Abu AB
    Bull Environ Contam Toxicol, 1993 Mar;50(3):413-6.
    PMID: 8428121
    Matched MeSH terms: Diatoms/drug effects*
  15. Fulltext Metabolite Profiling of the Microalgal Diatom Chaetoceros Calcitrans and Correlation with Antioxidant and Nitric Oxide Inhibitory Activities via ¹H NMR-Based Metabolomics
    Azizan A, Ahamad Bustamam MS, Maulidiani M, Shaari K, Ismail IS, Nagao N, et al.
    Mar Drugs, 2018 May 07;16(5).
    PMID: 29735927 DOI: 10.3390/md16050154
    Microalgae are promising candidate resources from marine ecology for health-improving effects. Metabolite profiling of the microalgal diatom, Chaetoceros calcitrans was conducted by using robust metabolomics tools, namely ¹H nuclear magnetic resonance (NMR) spectroscopy coupled with multivariate data analysis (MVDA). The unsupervised data analysis, using principal component analysis (PCA), resolved the five types of extracts made by solvents ranging from polar to non-polar into five different clusters. Collectively, with various extraction solvents, 11 amino acids, cholesterol, 6 fatty acids, 2 sugars, 1 osmolyte, 6 carotenoids and 2 chlorophyll pigments were identified. The fatty acids and both carotenoid pigments as well as chlorophyll, were observed in the extracts made from medium polar (acetone, chloroform) and non-polar (hexane) solvents. It is suggested that the compounds were the characteristic markers that influenced the separation between the clusters. Based on partial least square (PLS) analysis, fucoxanthin, astaxanthin, violaxanthin, zeaxanthin, canthaxanthin, and lutein displayed strong correlation to 2,2-diphenyl-1-picrylhydrazyl (DPPH) free radical scavenging and nitric oxide (NO) inhibitory activity. This metabolomics study showed that solvent extractions are one of the main bottlenecks for the maximum recovery of bioactive microalgal compounds and could be a better source of natural antioxidants due to a high value of metabolites.
    Matched MeSH terms: Diatoms/metabolism*
  16. Variation partitioning of benthic diatom community matrices: Effects of multiple variables on benthic diatom communities in an Austral temperate river system
    Dalu T, Wasserman RJ, Magoro ML, Mwedzi T, Froneman PW, Weyl OLF
    Sci Total Environ, 2017 Dec 01;601-602:73-82.
    PMID: 28551541 DOI: 10.1016/j.scitotenv.2017.05.162
    This study explores diatom community dynamics in a highly modified semi-arid temperate region river system characterised by inconsistent river flow. Various water and sediment environmental variables were assessed using a multi-faceted analysis approach to determine the spatio-temporal drivers of benthic diatom communities in the river system. Overall, the diatom community was generally dominated by pollution tolerant species, reflecting the anthropogenic intensity and activities on the river system. Diatom community composition was found to be largely determined by water column chemistry variables particularly nutrient concentrations in comparison to sediment chemistry and physical variables. Strong seasonal diatom species composition was also observed and this was driven by strong seasonal variations in nutrient loads and metal concentrations, a result of the variable water flow across the two seasons. However, the greater temporal variation in communities was observed in the smaller systems with the mainstream river system being more homogenous over time. In addition, diatom community composition and environmental variables were found to be different and more pronounced between streams and mainstream sites, than between canals and streams. The study highlights the complex interaction between water column, sediment and physical variables in determining the diatom species composition in small river systems. It also highlights the importance of river flow inconsistency as an indirect variable that alters primary drivers such as nutrient concentrations in the water column and heavy metal levels in the sediment.
    Matched MeSH terms: Diatoms/growth & development*
  17. Fulltext Dominant phytoplankton groups as the major source of polyunsaturated fatty acids for hilsa (Tenualosa ilisha) in the Meghna estuary Bangladesh
    Shaha DC, Hasan J, Kundu SR, Yusoff FM, Salam MA, Khan M, et al.
    Sci Rep, 2022 Dec 05;12(1):20980.
    PMID: 36470973 DOI: 10.1038/s41598-022-24500-2
    The tropical estuarine ecosystem is fascinating for studying the dynamics of water quality and phytoplankton diversity due to its frequently changing hydrological conditions. Most importantly, phytoplankton is the main supplier of ω3 polyunsaturated fatty acids (PUFA) in the coastal food web for fish as they could not synthesize PUFA. This study evaluated seasonal variations of water quality parameters in the Meghna River estuary (MRE), explored how phytoplankton diversity changes according to hydro-chemical parameters, and identified the major phytoplankton groups as the main source of PUFA for hilsa fish. Ten water quality indicators including temperature, dissolved oxygen, pH, salinity, dissolved inorganic nitrogen (DIN = nitrate, nitrite, ammonia) and phosphorus, dissolved silica and chlorophyll-a were evaluated. In addition, phytoplankton diversity was assessed in the water and hilsa fish gut. Principal component analysis (PCA) was used to analyze the spatio-temporal changes in the water quality conditions, and the driving factors in the MRE. Four main components were extracted and explained 75.4% variability of water quality parameters. The most relevant driving factors were dissolved oxygen, salinity, temperature, and DIN (nitrate, nitrite and ammonia). These variabilities in physicochemical parameters and dissolved inorganic nutrients caused seasonal variations in two major groups of phytoplankton. Peak abundance of Chlorophyta (green algae) occurred in water in nutrient-rich environments (nitrogen and phosphorus) during the wet (36%) season, while Bacillariophyta (diatoms) were dominant during the dry (32%) season that depleted dissolved silica. Thus, the decrease of green algae and the increase of diatoms in the dry season indicated the potential link to seasonal changes of hydro-chemical parameters. The green algae (53.7%) were the dominant phytoplankton group in the hilsa gut content followed by diatoms (22.6%) and both are contributing as the major source of PUFAs for hilsa fish according to the electivity index as they contain the highest amounts of PUFAs (60 and 28% respectively).
    Matched MeSH terms: Diatoms*
  18. A non-toxigenic but morphologically and phylogenetically distinct new species of Pseudo-nitzschia, P. sabit sp. nov. (Bacillariophyceae)
    Teng ST, Lim PT, Lim HC, Rivera-Vilarelle M, Quijano-Scheggia S, Takata Y, et al.
    J Phycol, 2015 Aug;51(4):706-25.
    PMID: 26986792 DOI: 10.1111/jpy.12313
    A new species of Pseudo-nitzschia (Bacillariophyceae) is described from plankton samples collected from Port Dickson (Malacca Strait, Malaysia) and Manzanillo Bay (Colima, Mexico). The species possesses a distinctive falcate cell valve, from which they form sickle-like colonies in both environmental samples and cultured strains. Detailed observation of frustules under TEM revealed ultrastructure that closely resembles P. decipiens, yet the new species differs by the valve shape and greater ranges of striae and poroid densities. The species is readily distinguished from the curve-shaped P. subcurvata by the presence of a central interspace. The morphological distinction is further supported by phylogenetic discrimination. We sequenced and analyzed the nuclear ribosomal RNA genes in the LSU and the second internal transcribed spacer, including its secondary structure, to infer the phylogenetic relationship of the new species with its closest relatives. The results revealed a distinct lineage of the new species, forming a sister cluster with its related species, P. decipiens and P. galaxiae, but not with P. subcurvata. We examined the domoic acid (DA) production of five cultured strains from Malaysia by Liquid chromatography-mass spectrometry (LC-MS), but they showed no detectable DA. Here, we present the taxonomic description of the vegetative cells, document the sexual reproduction, and detail the molecular phylogenetics of Pseudo-nitzschia sabit sp. nov.
    Matched MeSH terms: Diatoms
  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: Diatoms
  20. Fulltext Elevated CO2 improves both lipid accumulation and growth rate in the glucose-6-phosphate dehydrogenase engineered Phaeodactylum tricornutum
    Wu S, Gu W, Huang A, Li Y, Kumar M, Lim PE, et al.
    Microb Cell Fact, 2019 Sep 23;18(1):161.
    PMID: 31547820 DOI: 10.1186/s12934-019-1214-x
    BACKGROUND: Numerous studies have shown that stress induction and genetic engineering can effectively increase lipid accumulation, but lead to a decrease of growth in the majority of microalgae. We previously found that elevated CO2 concentration increased lipid productivity as well as growth in Phaeodactylum tricornutum, along with an enhancement of the oxidative pentose phosphate pathway (OPPP) activity. The purpose of this work directed toward the verification of the critical role of glucose-6-phosphate dehydrogenase (G6PDH), the rate-limiting enzyme in the OPPP, in lipid accumulation in P. tricornutum and its simultaneous rapid growth rate under high-CO2 (0.15%) cultivation.

    RESULTS: In this study, G6PDH was identified as a target for algal strain improvement, wherein G6PDH gene was successfully overexpressed and antisense knockdown in P. tricornutum, and systematic comparisons of the photosynthesis performance, algal growth, lipid content, fatty acid profiles, NADPH production, G6PDH activity and transcriptional abundance were performed. The results showed that, due to the enhanced G6PDH activity, transcriptional abundance and NAPDH production, overexpression of G6PDH accompanied by high-CO2 cultivation resulted in a much higher of both lipid content and growth in P. tricornutum, while knockdown of G6PDH greatly decreased algal growth as well as lipid accumulation. In addition, the total proportions of saturated and unsaturated fatty acid, especially the polyunsaturated fatty acid eicosapentaenoic acid (EPA; C20:5, n-3), were highly increased in high-CO2 cultivated G6PDH overexpressed strains.

    CONCLUSIONS: The successful of overexpression and antisense knockdown of G6PDH well demonstrated the positive influence of G6PDH on algal growth and lipid accumulation in P. tricornutum. The improvement of algal growth, lipid content as well as polyunsaturated fatty acids in high-CO2 cultivated G6PDH overexpressed P. tricornutum suggested this G6PDH overexpression-high CO2 cultivation pattern provides an efficient and economical route for algal strain improvement to develop algal-based biodiesel production.

    Matched MeSH terms: Diatoms
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