Morphology and molecular phylogeny of the marine diatom Nitzschia dentatum sp. nov. and N. Johorensis sp. nov. (Bacillariophyceae) from Malaysia

The marine diatom Nitzschia dentatum sp. nov. isolated from seawater samples of Kudat and N. johorensis sp. nov. isolated from beach sand samples of Sibu Island, Malaysia, have been described in this paper. Morphological identification, molecular phylogeny and toxin analyses were executed on the pure non-axenic algal cultures designated as KD89 and PS8, respectively. The main distinguishing feature of N. dentatum sp. nov. compared to other species is the jaggedcingulum structure which is only unique to this species. Meanwhile, N. johorensis sp. nov.is strongly characterized by the 'hantzschioid'and 'nitzschioid' symmetry dimorphisms; a common diagnostic feature but rarely described in other Nitzschia species. Identification of both strains was made based on the frustule diagnostic features and verified using the partial large ribosomal subunit DNA sequences. The results have confirmed that these two speciesare independent entities and novel species that have not been documented elsewhere. A notable finding from the Maximum Likelihood (ML), Maximum Parsimony (MP) and Bayesian Index (BI) analyses have also revealed that Nitzschia species that have indentation in the middle of valves have been consistently grouped as same clade with high bootstrap values. The extracts of both species did not show detectable amount of domoicacid and have therefore, been classified as non-toxic. This discovery contributes to the documentation of Nitzschia species worldwide

Studi Ketoksikan Dinoflagelata Spesies Prorocentrum Minimum (Dinophyceae) Schiller (Pavillard)

This study was carried out to determine the toxicity of the dinoflagellate Prorocentrum minimum species that formed massive blooms in Lido Beach, Johor Bahru in July 2002. Clone cultures were established in ES-DK medium at 26o C under a 14:10 hour light dark cycle. Species toxicity was determined by intra peritoneal (i.p) injection of culture extract into mice. Cultured cell extracts were toxic to mice. The major symptoms were muscular paralysis and diarrhea. However no mouse mortality was observed even after 13 hours. Extracts of cultured cells were also hemolytic on rabbit red blood cells. Keywords: Dinoflagellate, HAB, Prorocentrum minimum, Red Tide dan Toxicity Kajian dilakukan untuk menentukan ketoksikan dinoflagelata spesies Prorocentrum minimum yang menyebabkan kejadian pasang merah besar-besaran di perairan Pantai Lido, Johor Bahru pada Juli tahun 2002. Kultur klon telah dibuat dalam medium ES-DK pada suhu 26o C dan siklus pencahayaan 14:10 jam terang gelap. Ketoksikan spesies diuji dengan penyuntikan ekstrak kultur secara intra peritoneal (i

Sulfate-reducing bacteria metabolite detection using GC-MS

This research was conducted to investigate and compare the various metabolite, produced from the metabolism of two different SRB strain, that were involved in the biocorrosion process. Stainless steel coupons were immersed in two strains of sulfatereducing bacteria, A1H1 and EB3 (designated as SRB1 and SRB2 repectively) were isolated from Port Dickson marine vicinity that were grown in VMNI medium. The immersion period were set for eight days. Analysis of Gas Chromatography-Mass Spectrometry (GC-MS) was conducted using –trimethylsilyl (TMS) of N-methyl-N-trimethylsilylfluoracetamide (MSTFA). The data were than analyzed using Partial Least Squares Discriminant Analysis (PLS-DA) method to discriminate the unique metabolite according to each strain. The result showed that SRB1 generates less metabolite but high in concentration. Meanwhile, SRB2 shows a variety production of metabolites but less in concentration. Both strains share the same metabolism in the production of nitrogen based substance and production of norvaline and pentanoic acid. SRB1 shows a very distinct feature as the production of ribitol was spotted in its metabolism where it is usually associated with growth. SRB2 showed a very close usage of sulphur by production of methionine. These results suggest that different SRB strain produced different number and type of metabolites in the biocorrosion process

Morphology and molecular phylogeny of the marine diatom nitzschia dentatum sp. nov and N. Johorensis sp. nov ( bacillariophyceae) from Malaysia

The marine diatom Nitzschia dentatum sp. nov. isolated from seawater samples of Kudat and N. johorensis sp. nov. isolated from beach sand samples of Sibu Island, Malaysia, have been described in this paper. Morphological identification, molecular phylogeny and toxin analyses were executed on the pure non-axenic algal cultures designated as KD89 and PS8, respectively. The main distinguishing feature of N. dentatum sp. nov. compared to other species is the jaggedcingulum structure which is only unique to this species. Meanwhile, N. johorensis sp. nov. is strongly characterized by the `hantzschioid'and `nitzschioid' symmetry dimorphisms; a common diagnostic feature but rarely described in other Nitzschia species. Identification of both strains was made based on the frustule diagnostic features and verified using the partial large ribosomal subunit DNA sequences. The results have confirmed that these two speciesare independent entities and novel species that have not been documented elsewhere. A notable finding from the Maximum Likelihood (ML), Maximum Parsimony (MP) and Bayesian Index (BI) analyses have also revealed that Nitzschia species that have indentation in the middle of valves have been consistently grouped as same clade with high bootstrap values. The extracts of both species did not show detectable amount of domoicacid and have therefore, been classified as non-toxic. This discovery contributes to the documentation of Nitzschia species worldwide

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

Harmful Algal Blooms. A scientific summary for policy makers

What is a Harmful Algal Bloom (HAB)? Photosynthetic algae support healthy aquatic ecosystems by forming the base of the food web, fixing carbon and producing oxygen. Under certain circumstances, some species can form high-biomass and/or toxic proliferations of cells (or “blooms”), thereby causing harm to aquatic ecosystems, including plants and animals, and to humans via direct exposure to water-borne toxins or by toxic seafood consumption. Ecosystem damage by high-biomass blooms may include, for instance, disruption of food webs, fish-killing by gill damage, or contribution to low oxygen “dead-zones” after bloom degradation. Some species also produce potent natural chemicals (toxins) that can persist in the water or enter the food web, leading to illness or death of aquatic animals and/or human seafood consumers

Comparison of biofilms morphology for two strains of marine sulfate-reducing bacteria using atomic force microscopy

AISI 304 stainless steel coupons were immersed in VMNI medium containing two strains of Sulfate-reducing bacteria which were isolated from Port Dickson, Negeri Sembilan. The immersion period were set for twenty-four hour, seven days, nine days and fifteen days. At the end of each period, the biofilm were formed on the surface will be maps using Atomic Force Microscopy. The image were taken using contact mode in the 70 μm x 70 μm and 10 μm x 10 μm resolution. Bacteria counts were done using the dilution and plate count technique. Image showed that SRB2 contain more bacteria cell attached to the metal surface by the 7th day of immersion compare to SRB1. But SRB1 produce more condensed and slime like biofilm with some crystallization precipitation while SRB2 bacteria cell were loosely attached. SRB1 bacteria cell were engulf in the slime like matrix while SRB2 bacteria cell is densely packed together. SRB2 showed a slightly higher rate growth in the medium compared to SRB1 but produce low amount of biofilm matrix while SRB1 produce a lot of bio-matrix precipitation and slime formation

Electrochemical impedance spectroscopy studies of stainless steel corrosion by two strains marine sulfate reducing bacteria

This research was conducted to compare corrosion potential of two strains of marine sulfate reducing bacteria (SRB1 and SRB2) on their effect of biocorrosion on stainless steel AISI304 using electrochemical techniques. This study was carried out using Electrochemical Impedance Spectroscopy (EIS) to determine the impedance value (passivity, Rp) and corrosion rate. An electrochemical measurement showed that the value of Impedance for Stainless steel in SRB culture is much smaller compare to VMNI medium (control), indicating a degradation of metal was occurred. SRB2 showed more aggressiveness on corrosion compare to SRB1 as the impedance value, Rp of stainless steel in SRB2 culture is lower compare to SRB1. In conclusion, EIS techniques given a good results to study mechanisms of corrosion and surface passivity