Date of Award
Honors College Thesis
The dinoflagellate K. brevis is a mixotrophic marine alga that is of ecological importance in coastal waters especially along the Gulf of Mexico. They are one of a few species of algae responsible for the production of “harmful algae blooms” or HABs in which they release neurotoxins called brevetoxins which negatively impact fishing industries, local wildlife, tourism, and coastal health. Because of the danger these algae pose their lifecycle and characteristics merit intensive study.
During a previous experiment in Dr. McLean’s lab involving salinity stressing cultured K. brevis, the stressed cultures exhibited an unusual data pattern when having their ribosomal RNA profile bioanalyzed. The rRNA pattern for these stressed cultures showed an additional set of rRNA bands that were absent in all healthy non-shocked cultures, one smaller than the K. brevis small ribosomal subunit and one larger than the K. brevis large ribosomal subunit. Cultures of K. brevis that were bioanalyzed before shocking and after shocking clearly showed the anomalous rRNA bands appearing directly after stressing.
Looking at the stressed cells under a light microscope revealed that the stressed cells had their membranes pinching off in small bubbles with what looked like small motile agents moving about within. Because intracellular organisms are known to inhabit other dinoflagellates we believe that the second set of rRNA signals and movement within stressed cells could be explained by an intracellular parasite or mutualistic symbiote that remains dormant until its host begins to die.
In order to test if an intracellular organism was actually the source of the abnormal rRNA data a variety of tests were applied to stressed K. brevis cultures. Lugol staining, DAPI staining, PCR amplification, microscopy and cloning were all used in an attempt to find any indication of a candidate organism. Despite all initial observations and data being consistent with an intracellular organism these later tests effectively disproved the initial hypothesis. Because the new data makes the intracellular organism explanation unlikely the source of the anomalous rRNA bands during stressing remains unknown.
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McArthur, Daniel O., "Identification of an Unknown Intracellular Organism in Karenia brevis" (2013). Honors Theses. 161.