Issue 7, Spring 2009

The effects of heat and oxidative stress on immunocompetence in cnidarians

Claire Campbell, Thomas Bartlett, Lisa May, Cheryl Woodley

In the last two decades, coral reefs have rapidly declined due to a combination of environmental, microbial, and anthropogenic stressors. Though little is known regarding coral innate immunity, these cnidarians have the ability to produce antimicrobial peptides (AMPs) that kill or interfere with the growth of bacteria, fungi, and viruses. This study quantifies AMP activity using an IMCOMP-P (immuno-competence-permeability) and liquid growth inhibition assay from protein extracts from a cnidarian model system, Nematostella vectensis, against a known coral pathogen, Serratia marcescens. Experimental animals were subjected to two treatments including temperatures exceeding 37°C and increasing concentrations of exogenous hydrogen peroxide (1 µM, 100 µM) to simulate heat and oxidative stress, respectively. In the heat stress experiment, AMP activity increased in the control resulting in lower bacterial growth compared to the stress treatment. The control in the oxidative stress experiment also resulted in the highest AMP activity, while AMP activity decreased in the 1 µM concentration. Since no statistically significant differences were observed between treatments in either assay, these results suggest that the experimental conditions were not sufficient to induce a significant difference in AMP activity. Observations from this study indicate that N. vectensis may serve as a beneficial comparative organism in studies related to abiotic and biotic stressors and AMP production in corals.

Keywords: Nematostella vectensis, Serratia marcescens, oxidative stress, heat stress, antimicrobial peptides, immunocompetence