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Liz Vallen

Howard A. Schneiderman '48 Professorship in Biology

On Leave



  2. Phone: (610) 328-8048
  3. Maxine Frank Singer '52 Hall 310
Elizabeth Vallen

Publications | Research | Student Abstracts



BIOL 1. Cellular and Molecular Biology. Team taught. An introduction to the study of living systems illustrated by examples drawn from cell biology, biochemistry, genetics, microbiology, neurobiology, and developmental biology. 
BIOL 14. Cell Biology. A study of the ultrastructure, molecular interactions, and function of cell components, focusing primarily on eukaryotic cells. Topics include protein and membrane structure, organelle function and maintenance, and the role of the cytoskeleton. syllabus [pdf]

BIOL 114. Symbiotic Interactions. This seminar will focus on the molecular basis of plant-microbe, animal-microbe, and possibly microbe-microbe symbioses. In addition to studying specific systems, common themes and pathways will be analyzed and discussed (nutrient exchange, suppression of the immune response, specificity of host-symbiont recognition, etc.). Readings will be primarily from the research literature. Laboratory projects will use molecular techniques and likely focus on the sea anemone Aiptasia and its symbiotic, photosynthetic dinoflagellate, Symbiodinium. syllabus [pdf]


Confocal image of a cross section of the tentacles and oral disk (bottom right) in Aiptasia pallida. Symbiotic dinoflagellates autofluoresce red and nuclei are visualized with the dye TOTO (green). Replicating DNA was visualized by incorporation of EdU (blue). Julia Berthet '10

After studying various aspects of cell division in the yeast, Saccharomyces cerevisiae, I became very interested in the interactions between cnidarians (coral, sea anemones) and their intracellular symbiotic algae of the genus Symbiodinium. This relationship is essential for the growth of corals and its breakdown, known as coral "bleaching," can result in the collapse of entire reef ecosystems.
My long-term objective is to understand the cell biological events that occur upon the onset, maintenance and breakdown of the symbiotic relationship between cnidarians (corals and sea anemones) and photosynthetic algae. The algae are phagocytosed from seawater and appear to evade the host immune response and alter subcellular trafficking to allow their intracellular persistence. The algae use energy from sunlight to make sugars from carbon dioxide and water, and give up to 90% of this sugar to the coral or anemone host.

We primarily study the interaction between the algae and cnidarian host using the sea anemone, Aiptasia pallida. Aiptasia can be cultured easily in the laboratory and it propagates asexually, allowing the generation of clonal populations. We can keep both symbiotic and aposymbiotic (bleached) organisms in the lab, allowing a variety of experimental comparisons and manipulations.

My recent sabbatical at Kewalo Marine Laboratory was funded by the NSF and NIH.

Currently, in my lab at Swarthmore College, we are primarily focused on two projects.

1. How to accommodate cells within your cells?  Changes in the cnidarian cytoskeleton in the presence of Symbiodinium.

(Some of this work was presented at the International Symbiosis Society meeting, August 2009)

Sara Kim '11 (NYU Medical School), Erin Scanlon '10 (research assistant at the University of Pennsylvania), Frances Taschuk '10 (research assistant at the University of Michigan), and Farah Hussain '09 (SUNY Downstate Medical School). 
A confocal image of the symbiotic zooxanthellae Symbiodinium (red autofluorescence) in the tentacles of the sea anemone Aiptasia pallida (microtubules stained green).  Sara Kim ’11
Read Farah Hussain's honors thesis abstract here.
cytoskeletal adhesion protein
A cytoskeletal adhesion protein with a possible role in reshaping the cytoskeleton during infection and/or expulsion of Symbiodinium, green; autofluorescent Symbiodinium, red.  Erin Scanlon '10 and Sara Kim '11


2. Cell proliferation in the symbiotic cnidarian Aiptasia pallida: which cells are replicating their DNA?
 (Some of this work was presented at the International Symbiosis Society meeting, August 2009)  
Julia Berthet '10 (research assistant at the Wyss Institute at Harvard University) and Ian Yarett '09 (Newsweek Magazine)
Read Ian Yarett's and Julia Berthet's honors theses abstracts here.


Courses | Publications | Research | Student Abstracts