ASSESSING ENVIRONMENTAL CONTROLS AND BIOGEOCHEMICAL CONSEQUENCES OF VIRUS-HOST INTERACTIONS IN MARINE EUKARYOTIC PICOPHYTOPLANKTON

Abstract:

Viruses are the most abundant biological entities in marine systems and propagate through lysis of their prokaryotic or eukaryotic hosts. Viruses infecting marine phytoplankton can be significant agents of mortality and disrupt the canonical flow of carbon and nutrients through the microbial loop via the “viral shunt.” A large proportion of the ocean’s primary production is contributed by photosynthetic eukaryotes, which are important members of the picophytoplankton size class. The smallest picoeukaryote Ostreococcus represents a diverse and widely distributed genus. While the genomes of several viruses infecting the coastal species Ostreococcus lucimarinus have been sequenced, the dependence of viral infection dynamics on environmental parameters such as light and nutrient availability has not been characterized. Therefore, the goal of this study is to determine how light synchronization and nutrient availability modulate the infection of three O. lucimarinus viruses. Viruses were introduced to mid-exponentially-growing O. lucimarinus cultures at different points during a 14:10h light:dark cycle and the infections were followed through a lysis event. Additionally, viral infection dynamics were quantified for cultures of O. lucimarinus under either nutrient-replete or nutrient-deplete conditions. Preliminary results suggest that both light and nutrient availability influence viral infection dynamics, and that low nutrient availability may dampen the severity of infection. This work provides insight to the role of light and nutrient availability in controlling viral replication in an ecologically important picophytoplankton. Considering virus-host interactions is therefore critical for understanding marine plankton-driven biogeochemical processes.