VIRAL INFECTION OF EMILIANIA HUXLEYI (PRYMNESIOPHYCEAE) LEADS TO ELEVATED PRODUCTION OF REACTIVE OXYGEN SPECIES¹

<jats:p>The effect of viral infection of <jats:italic>Emiliania huxleyi</jats:italic> (Lohman) Hay and Mohler on the concentration of intracellular reactive oxygen species (ROS), hydrogen peroxide (H<jats:sub>2</jats:sub>O<jats:sub>2</jats:sub>) excretion and cell photosynthetic capacity (CPC) was examined. During the crash of an <jats:italic>E. huxleyi</jats:italic> culture induced by viruses intracellular ROS concentrations were generally elevated and reached levels of approximately double those observed in non‐infected control cultures. H<jats:sub>2</jats:sub>O<jats:sub>2</jats:sub> concentrations also increased in the media of the infected cultures from background levels of around 130 nM to approximately 580 nM while levels in the controls decreased. These data suggest that oxidative stress is elevated in infected cells. Although the precise mechanism for ROS production was not identified, a traditional defense related oxidative burst was ruled out, as no evidence of a rapid intracellular accumulation of ROS following addition of the virus was found. CPC declined substantially in the infected culture from a healthy 0.6–0 arbitrary units. Clearly infection disrupted normal photosynthetic processes, which could lead to the production of ROS via interruption of the electron transport chain at the PSII level. Alternatively, ROS may also be a necessary requirement for viral replication in <jats:italic>E. huxleyi</jats:italic>, possibly due to a link with viral‐induced cell death or associated with general death processes.</jats:p>