Document Type

Dissertation

Degree

Doctor of Philosophy (PhD)

Department

Chemistry

First Advisor's Name

Kathleen Rein

First Advisor's Committee Title

committee chair

Second Advisor's Name

Yuan Liu

Second Advisor's Committee Title

committee member

Third Advisor's Name

Xiaotang Wang

Third Advisor's Committee Title

committee member

Fourth Advisor's Name

Jose M. Eirin-Lopez

Fourth Advisor's Committee Title

committee member

Fifth Advisor's Name

Rudolf Jaffe

Fifth Advisor's Committee Title

committee member

Keywords

Karenia brevis, brevetoxin, Receptors, Thioredoxin, Thioredoxin reductase, Harmful algal blooms, Antioxidant, Inhibition

Date of Defense

11-7-2016

Abstract

Algae are important to marine and fresh-water ecosystems. However, some species of algae are harmful or even toxic. They can consume oxygen or block sunlight that is essential for other organisms to live. Indeed, some algae blooms can produce toxins that damage the health of the environment, plants, animals, and humans. Harmful algal blooms (HABs) which are often more green, brown, or dark-colored than red have spread along the coastlines and in the surface waters of the United States. Therefore, scientists are making great efforts to study HABs in order to maintain human and ecosystem health.

Karenia brevis, the major harmful algal bloom dinoflagellate of the Gulf of Mexico, plays a destructive role in the region. Karenia brevis, responsible for Florida red tide, is the principle HAB dinoflagellate in the Gulf of Mexico. K. brevis blooms can produce brevetoxin: ladder-shaped polyether (LSP) compounds, which can lead to adverse human health effects, like reduced respiratory function through inhalation exposure, or neurotoxic shellfish poisoning through consumption of contaminated shellfish. The poisoning has been attributed to their affinity for voltage-sensitive sodium ion channels causing channel opening and depolarization of excitable cell membranes. Conservative estimate suggests that the economic impact from all harmful algal bloom events in the United States is at least $82 million/year. The public health costs occupy $37 million alone.

The study presented herein utilized fluorescent and photolabile brevetoxin probes to demonstrate that brevetoxin localizes in the chloroplast of K. brevis where it binds to light harvest complex II (LHC II) and thioredoxin (Trx). It had been discovered that the TrxR/Trx system was inhibited by brevetoxin-2 (PbTx-2) with an IC50 of 25 µM. The mechanism of the inhibition was discussed in this work. The research also revealed that the K. brevis high-toxic and low-toxic strains have a significant difference in their ability, not only to produce brevetoxin, but also to perform NPQ and in the production of ROS. I compared and contrasted various metabolic and biochemical parameters in two strains of K. brevis which had a ten-fold difference in toxin content. The work could shed light on the physiological role that brevetoxin fills for K. brevis and may contribute to understanding the effect of ladder-shaped polyether compounds on both marine animals and exposed humans and shall inform improved treatments for brevetoxicosis.

Identifier

FIDC001236

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