<i>Karenia</i> species in the Gulf of Mexico: Cell Cycle Characterization and Development of a Novel Tool for Species Specific Protein Analysis
Harmful algal blooms of <i>Karenia</i> species have been documented in the Gulf of Mexico for over a century. At least four species are known to co-occur in blooms: <i>Karenia brevis</i>, <i>Karenia mikimotoi</i>, <i>Karenia papilionacea</i>, and <i>Karenia selliformis</i>. The first objective of this study was to characterize the cell cycle progression of each <i>Karenia</i> species, and examine their expression of the cell cycle-specific protein proliferating cell nuclear antigen (PCNA) over the diel cycle. This work found that all four species exhibited diel phasing of their cell cycles, and observed a strong significant relationship between PCNA and S-phase of the cell cycle in <i>K. brevis</i>, <i>K. mikimotoi</i> and <i>K. selliformis</i> (p ≤ 0.01), as well as a less significant relationship in <i>K. papilionacea</i> (p < 0.10) These results indicate the potential for the use of PCNA in a species-specific growth assay. The second objective of this study further examined the relationship between PCNA abundance and growth rates in <i>K. brevis</i> using flow cytometry to quantify PCNA abundance, but found no significant relationship, possibly due to the differing epitope cross-reactivity of a newly synthesized PCNA antibody. A dual labeling method was designed combining a <i>K. brevis</i> specific fluorescent in-situ hybridization (FISH) probe and the PCNA antibody to analyze intracellular protein in a species-specific method. This is the first report of such a dual labeling technique in a phytoplankton species, and the method has many potential applications for phytoplankton research. Its utility in <i>Karenia</i> species, for species-specific growth rate determination remains viable, but would require a more effective PCNA antibody.