Phytoplankton are phototrophic organisms that are the main contributors to marine primary production. My project investigated ribosomal RNA (rRNA) gene content and its relationship to phytoplankton physiology, using the toxic dinoflagellate Alexandrium tamarense as a model. Ribosomal RNA is essential to the cell because it provides structure for ribosomes. There have been published and unpublished studies demonstrating that the rRNA gene copy number in phytoplankton cells changes over the growth cycle. For this project, quantitative PCR (qPCR) was used to analyze the rRNA gene content of the phytoplankton dinoflagellate Alexandrium tamarense. The rRNA gene content was analyzed from two different treatments: 1. samples collected from different growth stages; 2. samples collected from cultures grown with different amount of light, to see if there is a relation between growth rate and rRNA gene copy number. The growth stages used for the first experiment were early and late exponential, and three light levels were used for the second experiment.
The results show a difference in rRNA gene content between early and late exponential stage. The results contradict what has been seen in previous published studies. Additionally, variability in rRNA gene content was observed from the different levels of light. This raises the possibility that the change in gene copy number is related to physiological conditions.