Browsing by Subject "dinoflagellates"
Now showing 1 - 2 of 2
Results Per Page
Sort Options
Item Brevetoxin: How Is It Made and Why(2012-10-19) Thompson, NatalieKarenia brevis is the major harmful algal bloom-forming species in the Gulf of Mexico, and produces neurotoxins, known as brevetoxins, that cause large fish kills, neurotoxic shellfish poisoning, and human respiratory distress. Brevetoxins are polyethers that bind voltage-sensitive sodium channels, opening them for prolonged periods of time. Clonal cultures of K. brevis exhibit unique brevetoxin profiles, which not only differ from one another, but also change when subjected to different environmental conditions. The brevetoxin structures were elucidated 30 years ago without any breakthroughs for the biosynthetic pathway. These unique ladder-like polyethers have 10 (PbTx-1) or 11 (PbTx-2) rings, indicating that they are synthesized as secondary metabolites by polyketide synthases. The extensive size of the genome and the lack of histones and nucleosomes combined with the additional regulatory step of a trans-splicing spliced leader sequence make normal molecular techniques ineffective in determining the genes involved in toxin synthesis. The goal of this project is to identify a potential link between toxin, gene, and function. One objective is to take the next step towards identifying the genes associated with the synthesis and regulation of brevetoxins and to help elucidate the hypothesized gene clusters of multi-protein enzymatic complexes involved in brevetoxin production, one for each backbone. The second objective is to make an effort to determine the in vivo function of the costly brevetoxins by identifying possible ion channels, which could be osmotically regulated by the toxins. Genes for polyketide synthases (PKS) were identified in K. brevis, obtained from Expressed Sequence Tag (EST) libraries. In this work, reverse transcription polymerase chain reactions (RT-PCR) were used to generate pools of complementary DNA (cDNA), which was used in real-time quantitative polymerase chain reactions (qPCR) to give relative amounts of PKS transcripts. K. brevis clones have shown a significant increase in toxin production after a rapid shift from high salinity to low salinity, indicating a regulation of brevetoxin synthesis. To gain a better understanding of regulation of toxin production during algal blooms, we compared the toxin levels under different conditions to the transcript levels of PKS genes, as determined by quantitative RT-PCR. In a separate line of investigation, an in silico analysis of the EST library was performed to identify ion channel genes expressed by K. brevis, which may be the in vivo binding site of brevetoxin. The information generated from this project will help to elucidate the effects of environmental variations on toxin production and the biological function of toxin production -- valuable information for the shellfish industries and public health.Item Dinoflagellate Cyst Biostratigraphy, Palynofacies and Paleoenvironmental Analysis of the Maastrichtian and Basal Danian, Brazon River, Texas(2013-06-17) Aydin, TubaThis study aims to document the dinoflagellate cyst biostratigraphy and paleoenvironmental record of the Maastrichtian Neylandville and Corsicana Formations and the lower part of the Danian Kincaid Formation from the Brazos River, Texas. Rock samples are exposed to standard palynological methods for biostratigraphic interpretations. The quantitative data collected from palynological samples are combined with ?13C and ?18O stable isotope geochemistry and TEX86 and BIT Index organic geochemistry data for paleoenvironmental interpretations. Biostratigraphically important species of dinoflagellates divide the section into three intervals. Interval 1 occurs within the Neylandville Formation, and the presence of Alterbidinium acutulum, Xenascus ceratioides and Isabelidinium cooksoniae indicate that this interval is not younger than early Maastrichtian. Interval 2 represents the Corsicana Formation. The presence of the late Maastrichtian species Disphaerogena carposphaeropsis, Palynodinium grallator and Deflandrea galeata at the base of the Corsicana Formation indicate that this interval is of late Maastrichtian age. Interval 3 occurs within the Kincaid Formation. The presence of Carpetalla cornuta and Damassadinium californicum at the base of the Kincaid Formation indicates that this interval is of Danian age. Previously published Gulf of Mexico palynology studies, as well as planktonic foraminifera and nannoplankton data confirm the age assignments of the studied interval. Dinoflagellate species assemblages increase in diversity upwards from Interval 1 to Interval 2, and then show a small decrease above the K-Pg boundary within Interval 3, indicating that the K-Pg event was not catastrophic for the dinoflagellates. The Cerodinium spp. and Spiniferites spp. complex comprise a large proportion of the species within the section. High abundance peaks of Glaphyrocysta spp., Cribroperidinium spp., and Yolkinigymnium lanceolatum occur within Interval 2. Two intervals in the section are dominated by peridinioid dinoflagellates, measured by the Peridinioid/Gonyaulacoid (P/G) ratio. The first one occurs within Interval 2 and contains peaks of the P/G ratio that correlate with increases in ?13C, suggestive of an increase in paleoproductivity. Two more peaks occur within Interval 3. Bottom water ?18O temperatures determined from benthic foraminifera and sea surface temperatures determined from TEX86 organic geochemistry show an overall cooling trend from Early Maastrichtian to the K-Pg boundary.