UNIMAS Outstanding Online Course Award, 2009

UNIMAS Outstanding Online Course Award, 2009 is coferred to Dr. Leaw Chui Pin in recognition of your outstanding use of Morpheus in supporting your teaching. Organised by Centre for Applied Learning and Multimedia (CALM

Analysis of paralytic shellfish poisoning toxin congeners by a sodium channel receptor binding assay

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 tritiumlabeled STX for receptor sites on rat brain sodium channels. Competitive binding curves were described by a four-parameter logistic equation. Half-saturation values (EC50) 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 EC50 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

Matrix-Assisted Laser Desorption Ionization-Time of Flight Mass Spectrometry Identification of Yeasts Is Contingent on Robust Reference Spectra

BACKGROUND: Matrix-assisted laser desorption ionization-time of flight mass spectrometry (MALDI-TOF MS) for yeast identification is limited by the requirement for protein extraction and for robust reference spectra across yeast species in databases. We evaluated its ability to identify a range of yeasts in comparison with phenotypic methods. METHODS: MALDI-TOF MS was performed on 30 reference and 167 clinical isolates followed by prospective examination of 67 clinical strains in parallel with biochemical testing (total n = 264). Discordant/unreliable identifications were resolved by sequencing of the internal transcribed spacer region of the rRNA gene cluster. PRINCIPAL FINDINGS: Twenty (67%; 16 species), and 24 (80%) of 30 reference strains were identified to species, (spectral score ≥2.0) and genus (score ≥1.70)-level, respectively. Of clinical isolates, 140/167 (84%) strains were correctly identified with scores of ≥2.0 and 160/167 (96%) with scores of ≥1.70; amongst Candida spp. (n = 148), correct species assignment at scores of ≥2.0, and ≥1.70 was obtained for 86% and 96% isolates, respectively (vs. 76.4% by biochemical methods). Prospectively, species-level identification was achieved for 79% of isolates, whilst 91% and 94% of strains yielded scores of ≥1.90 and ≥1.70, respectively (100% isolates identified by biochemical methods). All test scores of 1.70-1.90 provided correct species assignment despite being identified to "genus-level". MALDI-TOF MS identified uncommon Candida spp., differentiated Candida parapsilosis from C. orthopsilosis and C. metapsilosis and distinguished between C. glabrata, C. nivariensis and C. bracarensis. Yeasts with scores of <1.70 were rare species such as C. nivariensis (3/10 strains) and C. bracarensis (n = 1) but included 4/12 Cryptococcus neoformans. There were no misidentifications. Four novel species-specific spectra were obtained. Protein extraction was essential for reliable results. CONCLUSIONS: MALDI-TOF MS enabled rapid, reliable identification of clinically-important yeasts. The addition of spectra to databases and reduction in identification scores required for species-level identification may improve its utility

Molecular phylogeny of tribe Schismatoglottideae (Araceae) based on two plastid markers and recognition of a new tribe, Philonotieae, from the neotropics

Tribe Schismatoglottideae comprises one large genus, Schismatoglottis, and six small ‘satellite’ genera. A combined molecular phylogenetic analysis of matK, the 3′ portion of the trnK intron, and trnL-F sequence data was carried out on 77 taxa representing all genera in the tribe, all informal groups in Schismatoglottis, together with sister tribe Cryptocoryneae, and outgroups from Araceae. Analyses of combined datasets with parsimony, maximum likelihood, and Bayesian methods revealed tribe Schismatoglottideae to be a polyphyletic assemblage. Neotropical Schismatoglottis is shown to be sister to the palaeotropical Schismatoglottideae + Cryptocoryneae. Schismatoglottis acuminatissima is a sister clade to the rest of the Schismatoglottideae. Palaeotropical Schismatoglottis is unsupported as a monophyletic genus. A new neotropical tribe of Araceae, Philonotieae S.Y. Wong & P.C. Boyce, sister to Cryptocoryneae + palaeotropical Schismatoglottideae, is proposed

Toxin profile and relative toxicity of three paralytic shellfish poisoning toxin- producing dinoflagellates from Malaysia

This study was carried out to determine the toxin profile and toxin content of Alexandrium minutum, Alexandrium tamiyavanichii and Pyrodinium bahamense var. compressum. These are three of the paralytic shellfish poisoning (PSP) toxin-producing marine dinoflagellates present in Malaysian waters. PSP toxins were analysed using an isocratic, post-column derivatization HPLC method with fluorescence detection. The three species differed significantly in toxin profile. A. minutum contained only GTX1, GTX2, ..

18S rDNA phylogeny of Pseudo-nitzschia (Bacillariophyceae) inferred from sequence-structure information

We explored the 18S rDNA sequences of Pseudo-nitzschia and its close relatives, together with their individual secondary structure information to reconstruct phylogenies. Forty-eight taxa classified in the Bacillariaceae and Achnanthaceae were analyzed by character-based (maximum parsimony and maximum likelihood) and distance-based (neighbour-joining) methods. Three raphid diatoms from the Eunotiaceae were used as out-groups. The sequencestructure alignment was generated by 4SALE (i.e. a one-letter encoded alignment that contained the individual secondary structure information) and applied to the character-based phylogeny reconstruction. All analyses highly support Pseudonitzschia + Fragilariopsis as monophyletic. The Pseudo-nitzschia/Fragilariopsis clade is further divided into three subclades. One clade comprises members in the P. seriata and P. americana complexes and species of Fragilariopsis; the second and third clades constitute members in P. pseudodelicatissima and P. delicatissima complexes. Among all analyses, the distance-based method yielded a more highly resolved phylogenetic framework for the Pseudo-nitzschia/Fragilariopsis clade than did the character-based analyses. Other than those currently known genetic markers, 18S rDNA was also useful in exploring the intrageneric relationships

Occurrence Of Three Alexandrium Species, A. Affine, A. Tamutum And A. Tamiyavanichii In Kuching Waters

A field survey was carried out in Kuching waters to monitor harmful microalgae in Kuching waters. Samples were collected fortnightly from Semariang Batu and Santubong estuaries during high tide. Live samples were used for culture establishment, while preserved samples were processed for morphological observation under epifluorescence microscopy. The occurrence of Alexandrium affine, A. tamutum and A. tamiyavanichii is reported for the first time in the coastal waters of Sarawak, with A. tamutum as a new record in Malaysian waters, which increased the number of Alexandrium species found to eight species. They are A. affine, A. leei, A. minutum, A. peruvianum, A. tamarense, A. tamiyavanichii, A. tamutum and A. taylori. This study has provided further information to the microalgae species inventory of the country

Toxicity of diatom Pseudo-nitzschia (Bacillariophyceae) analyzed using high performance liquid chromatography (HPLC)

Amnesic shellfish poisoning (ASP) is a type of shellfish poisoning due to the consumption of shellfish mollusks contaminated with domoic acid (DA). The toxin was first reported in the chain-forming pennate diatom, Pseudo-nitzschia and subsequently in other diatom species. In this study, clonal cultures of Pseudo-nitzschia were established from plankton samples collected from Sarawak and Sabah coastal waters. Clonal cultures were maintained in SWII medium with the addition of silicate at 25°C, 30 PSU and under 12:12 light-dark photoperiod. Fifteen milliliters of late exponential phase cultures were collected for toxin analysis and subsamples were taken for cell count. Cellular toxin was extracted by boiling in medium at 100°C for 5 minutes. The extracts were filtered to remove cell debris before being analyzed with HPLC using standard domoic acid, isodomoic A and B as reference toxins. All the 32 strains of Pseudo-nitzschia sp. analyzed in this study showed the absence of peaks corresponding to the three ASP toxins. This implies that non-toxic strains of Pseudo-nitzschia sp. are common in Malaysian waters. Further study will be carried out to include more strains along the coastal waters of Borneo as well as selected sites with shellfish farming activities in Peninsula Malaysia