SS2.03 Phytoplankton Ecology Using Molecular Approach
Date: Thursday, June 13, 2002
Time: 4:15:00 PM
Location: Colwood
 
JohnsonMD, University of Maryland, Center for Environmental Science, Horn Point Laboratory, Cambridge, USA, mjohnson@hpl.umces.edu
Stoecker, D, K, University of Maryland, Center for Environmental Science, Horn Point Laboratory, Cambridge, USA, stoecker@hpl.umces.edu
Oldach, D, W, Institute of Human Virology and University of Maryland, School of Medicine, Baltimore, USA, oldach@umbi.umd.edu
 
PHYLOGENETIC DIVERSITY OF CRYPTOPHYTE PLASTIDS IN THE CILIATE MESODINIUM RUBRUM AND INGESTION OF FLUORESCENTLY LABELED CRYPTOPHYTES
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Mesodinium rubrum is a common photosynthetic ciliate found in marine and estuarine habitats throughout the world. In Chesapeake Bay, M. rubrum is seldom abundant, but may reach densities greater than 5000 cells/ml in associated tributaries. The origin of plastids in M. rubrum, as permanent symbionts or temporarily sequestered from prey, is unclear. In an effort to understand the role of M. rubrum in aquatic ecosystems, two research projects were undertaken within the Pocomoke and Choptank Rivers: 1) grazing rates of M. rubrum on proflavine-labeled cryptomonads and 2) diversity of cryptomonad plastids found within M. rubrum. M. rubrum was found to ingest proflavine-labeled Pyrenomonas salina at low rates. To assess phylogenetic diversity of cryptomonad plastids, primers for the nucleomorph SSU rRNA gene were designed. Restriction fragment (RF) analysis of cloned PCR products revealed two RF-types within the Pocomoke River. Clones were sequenced for each. Preliminary analyses have revealed two distinct cryptophyte species in the Pocomoke River. Diversity of cryptophyte plastids within M. rubrum is being assessed by single-cell isolations and PCR, using cryptophyte-specific and universal-eukaryotic primers. These results are pending.