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Alexandra E. Purdy

Assistant Professor of Biology

Departmental affiliation: Biology


Host-microbe interactions; bacterial pathogenesis; marine microbiology; bacterial diversity and evolution; bacterial genetics


Courses in Fall 2012

Courses in Spring 2013

Courses in Fall 2013

Courses in Fall 2014

Courses in Spring 2015

Professional and Biographical Information

Submitted by Alexandra E. Purdy on Thursday, 3/20/2014, at 11:06 AM


Postdoctoral fellowship, Division of Infectious Diseases, Children’s Hospital Boston, Harvard Medical School (2008 – 2012)

Ph.D., Scripps Institution of Oceanography, University of California, San Diego, Marine Biology (2007)

B.S., College of William and Mary, Biology and Chemistry (2000)

 Research Interests

Many bacterial species use carefully regulated attachment and virulence mechanisms to colonize and sometimes sicken their eukaryotic hosts.  My laboratory aims to understand the complex molecular ‘conversations’ that underlie these interactions by studying Vibrio cholerae, the Gram-negative bacterium that causes cholera, an acute diarrheal disease that affects hundreds of thousands of people each year. 

Vibrio cholerae is naturally found in aquatic environments, often attached to phytoplankton, aquatic arthropods such as copepods, and larger organisms.  V. cholerae also can be carried by terrestrial arthropods such as houseflies.  Our laboratory explores interactions between V. cholerae and arthropods using Drosophila melanogaster, the common fruit fly, as a model system.  In the course of our work, we have discovered specific V. cholerae genes that are required for virulence and colonization in Drosophila.  These include genes that likely initiate signal transduction cascades that regulate expression of V. cholerae genes in the fly.  Our lab is interested in understanding how these regulatory cascades work; that is, what genes do they regulate?  What environmental signals do they sense?  How are they turned on and off? 

Ultimately, this project will reveal the genetic mechanisms that allow V. cholerae to associate with arthropods in order to survive and spread in the rivers, lakes, ponds, and oceans that let the disease persist in areas where it is endemic, and spread to distant locales.  Our ultimate goal is to better understand the ecology and evolution of a pathogen of major public health importance by integrating genomic, genetic, molecular and environmental approaches.

For more information about our lab, please take a look at our laboratory website. 

Teaching Interests

At Amherst, I am thrilled to be teaching Biol-271 Microbiology, a course that invites students to explore the world from a microbial point of view.  We seek to understand the diversity of ways in which microbes acquire energy, skirt immune responses, cause disease, rapidly adapt to change, and colonize almost every imaginable niche on the planet.  In the laboratory, we use classical and molecular microbiological techniques to explore this remarkable microbial diversity, and in the classroom we incorporate readings from the primary literature that highlight the most exciting recent findings in many areas of microbiology, including microbial genetics, genomics, pathogenesis, cell structure, ecology and diversity. 

I am also excited to be teaching a class for non-majors, Biol-110 Contagion, that focuses on mechanisms of bacterial and viral infectious disease and disease transmission.  We discuss the molecular biology of pathogenesis, but we also explore larger societal issues related to the burden of infectious disease today.  Most importantly, we will look at current attempts to halt the spread of infectious disease through medical and societal interventions and evaluate their successes and failures

My hope is that my students leave my classes with a deep appreciation and understanding for the critical roles that these unseen bacteria, archaea, and viruses play throughout their own lives, the lives of their fellow humans around the world, and the life of the planet.


Selected Publications

Purdy, A. E. and P. I. Watnick, 2011.  Spatially selective colonization of the arthropod intestine through activation of Vibrio cholerae biofilm formation. Proc. Natl. Acad. Sci. USA.  108:  19737-19742.

Purdy, A. E., D. Balch, M. L. Lizarraga-Partida, M. S. Islam, J. Martinez-Urtaza, A. Huq, R. R. Colwell, and D. H. Bartlett.  2010.  Diversity and distribution of cholix toxin, a novel ADP-ribosylating factor from Vibrio cholerae. Environ. Microbiol. Rep.  2(1):  198–207.

Jorgensen*, R., A. E. Purdy*, R. Fieldhouse, M. Kimber, D. H. Bartlett, and A. R. Merrill.  2008. Cholix toxin, a novel ADP-ribosylating factor from Vibrio cholerae.  J. Biol. Chem.  283:  10671-10678.   *These authors contributed equally.

Makri, S., A. E. Purdy, D. Bartlett, and J. Fierer.  2007.  Pathogenicity of environmental isolates of V. cholerae in mice. Microb. Infect.  9:  1351-1358.

Purdy, A., F. Rohwer, R. Edwards, F. Azam and D. H. Bartlett.  2005.  A glimpse into the genome content of the Vibrio cholerae species through identification of genes present in environmental strains.  J. Bacteriol. 187:  2992-3001.


Awards and Honors

NIH Ruth L. Kirschstein NRSA Individual Fellowship (2009 - 2011)

Peterson Fellowship, Scripps Institution of Oceanography (2007)

Howard Hughes Medical Institute Predoctoral Fellowship (2001 - 2006)

Claude ZoBell Fellowship, Scripps Institution of Oceanography (2001)   

Highest Honors in Biology, William & Mary (2000)

Charlotte P. Mangum Prize in Biology, William & Mary (2000)   

Phi Beta Kappa, William & Mary (1999)


Scholarly and Professional Activities

American Society for Microbiology, member

Association for Women in Science, member