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Daisy Marrero Colon - Protistan Ecology

University of Puerto Rico, Mayaguez 

Do Chaetoceros sp. Cultures Express Apoptosis During Viral Infection?

Diatoms are a major phytoplankton group that plays important roles in maintaining the oxygen levels in the atmosphere and the carbon cycle that sustains the primary nutritional production in the aquatic environments.  Among diatoms, the genus Chaetoceros is one of the most abundant and widespread; most of them are harmless and are considered to be the key primary photosynthetic producers that sustain higher forms of life.  Viruses that infect the genus Chaetoceros are widespread in Chesapeake Bay and may be an important source of mortality.  In laboratory cultures, viral infection of Chaetoceros leads to morphological changes in cell ultrastructure that resemble apoptosis, also called programmed cell death.  I my internship, I tested the hypothesis that viral infection of Chaetoceros sp. causes apoptosis.  To test that hypothesis, I induced viral infection in Chaetoceros cultures and then monitored the occurrence of caspase, an exzyme associated with apoptosis, over the infection cycle.  Chlorophyll fluorescence of Chaetoceros cultures inoculated with viruses decreased significantly with time, while that of uninfected control cultures increased, thus showing that viral inoculation produced infections.  No caspase-3 activity was detected in either infected or uninfected cultures, indicating that vial infection did not promote apoptosis.  These results suggest that infection of Chaetoceros in nature leads to release of new viruses, without inducing programmed cell death

Funding provided by the National Science Foundation – Research Experience for Undergraduates (REU)