Date of Award

1999

Document Type

Thesis

Department

Microbiology and Immunology

College

College of Graduate Studies

First Advisor

Karen Burnett

Second Advisor

Lou Burnett

Third Advisor

Thomas C. Siewicki

Fourth Advisor

Robert Kennedy

Fifth Advisor

Eric James

Abstract

Estuaries provide habitat and spawning grounds for numerous species of plants, birds, fish and shellfish. Levels of dissolved oxygen, carbon dioxide and pH in estuarine waters vary with diurnal, tidal and seasonal cycles. Anthropogenic factors may further exacerbate these variations in water quality. The studies presented here tested the hypothesis that hypoxia, including hypercapnia and acidosis, suppresses antibacterial defenses provided by phagocytic cells. The respiratory burst of phagocytic cells was stimulated with zymosan and Vibrio parahaemolyticus to produce Reactive Oxygen Species (ROS) which are potent antibacterial agents. The respiratory burst is oxygen dependent and therefore may be inhibited by hypoxic conditions. Hypoxic conditions within physiologically relevant conditions (Po2 = 15 Torr, Pco2 = 8.0 Torr, pH = 7.0) significantly suppressed ROS production measured by the luminol-enhanced chemiluminescence assay. Hypoxic conditions also significantly suppressed superoxide production, measured by the reduction of NBT, when stimulated with both zymosan and V. parahaemolyticus. Furthermore, while ROS mediated bactericidal activity was not significantly suppressed under hypoxia at the 1:1 phagocyte:bacterium ratio, there was a significant suppression when the bacterial challenge was increased to 1:10. It can be concluded from these results that hypoxia plays a critical role in maintaining antibacterial defense mechanisms of the mummichog, F. heteroclitus against the opportunistic marine pathogen V. parahaemolyticus.

Rights

All rights reserved. Copyright is held by the author.

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