Department of Biology, Swarthmore College
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Welcome to the Vollmer research lab

Mine is the only lab in the department that studies bacteria.  The focus of our investigations is bacterial stress response.  Our investigations include hypotheses and methods in genetics, physiology, biochemistry as well as in ecology and evolution.   Bacterial stress response is an area of expanding interest because it spans problems in infectious disease, environmental remediation, ecological consortia, biofilm establishment and long term evolutionary selection.  Since 1994, our laboratory has participated in and contributed to the Gordon Research Conference on Microbial Stress Response.   We also present posters at the General Meeting of the American Society for Microbiology in the Division I (General Microbiology) sessions on Microbial Stress Response.

Escherichia coli is the model system of choice.  It is the best characterized member of the prokaryotes, with a rich historic tradition as well as much current investigation.  This model system has provided paradigms for study in molecular genetics, bioenergetics, enzymology and bioinformatics.  There is a vast international network of scientists who contribute to this field.  In particular, response to stress involves:  the sensing of stress (external or internal to the cell); the transduction of the stress signal to regulators inside the cell; the induction of transcription of genes whose products serve to reduce the stress; restoration of a steady state balance in the cell; frequent cell-cell communication to coordinate a multicellular response; individual stochastic variation upon which natural selection operates

Many stress response pathways are well-conserved through the phyla, indicating an ancient evolutionary advantage for those organisms that were able to sense and respond to stress in a timely and strategic manner.  It should not be surprising that the mechanisms that all cells use to respond to stresses like heat shock, oxidative stress and DNA damage would be very homologous.  On the other hand, stresses that are more environmentally unique, like certain macro- or micro-nutrient limitations, have a more customized mechanism that suits a particular niche and organism.

A fundamental question that we are pursuing is how bacterial cells regulate the expression of a specific subset of stress response genes.  Our laboratory uses a bioluminescent reporter:  this allows us to measure the induction of transcription of a particular gene, by fusing a copy of the promoter of that gene to a group of lux genes.  The lux genes encode enzymes that work in a cycle and produce light as a by product of the chemical reactions.  This light can be quantified (linearly over 7 orders of magnitude) and in real time (so cells do not have to be broken open to measure the light).

A panel of bioluminescent stress-responsive E. coli strains were developed in collaboration with Robert LaRossa, Tina van Dyk and Shimshon Belkin while we were together at DuPont in the mid 1990s.  Since then, our laboratory has continued to construct new 'reporter' strains as well as to use those original strains in various environmental applications.  Some of the questions addressed in those studies were:

Can stress responsive bacteria be used to measure antioxidant activity found in green tea?

Can strains that respond to ammonia and phosphate limitation be used to measure the concentrations of those nutrients in the waters of the Chesapeake?

Does high frequency ultrasound kill bacteria?  And if, so, by what mechanisms?

Can ultrasound be used to sterile apple cider effectively?

Co optical tweezers induce oxidative stress or heat shock as cells are captured in the laser?

The ultrasound studies were conducted in collaboration with a colleague, Carr Everbach, in our Engineering Department.  The optical tweezers study was a conducted by a student who was jointly mentored by myself and a former member of the Department of Physics and Astronomy.

Another area of study in the laboratory has been on the role of Universal Stress Proteins in the regulation of stress response in E. coli.  These investigations have included the testing of various bioluminescent reporters in E. coli that are lacking the uspA, uspC and/or uspE genes.  In addition, we have studied biofilm formation and the influence that usp genes might have on adherence to plastic.

Previous undergraduate students in the laboratory, and their post-Swarthmore trajectory (If you want to update yours, contact me!)


class year

current or last known position

Meagan Bolles


MD/PhD student, UNC-Chapel Hill

Charlie Buffie


Res Asst, Northwestern Univ

Alexander Glick


Res Asst, Columbia Univ

Aparna Kishor*


Res Asst, NIH

Jawaad Hussain*


Medical student, SUNY

Melanie Johncilla


Res Asst, Univ of Penn

Jorge Aguilar*


Res Asst, Univ of Penn

Nicolle Gorby


Res asst, Northwestern Univ

Jeanne McFalls


Res Asst, Univ of Penn

Joanne Gaskell*


Res Asst, Internat'l Food Policy Res Inst

Krista Marshall


Med student, Univ. of Penn

Mathew So*


Med student, Mayo Clinic

Haena Kim


Med student, Univ of Pittsburgh

Semhar Mahmud


Med student, Temple Univ

Laura Valentine


Grad student, Univ of Wisconsin

Andrew Alderete


Res Asst, Univ of Penn

Cristina Cardemil


Med student, Univ of Penn

Clarissa Nobile


Grad student, Columbia Univ

Anne Willman Silk


Med student, Univ of Pittsburgh

Nathaniel Hanson


completed M.S., MIT

Andrew Caffrey*


Law student, Harvard Univ

Matthew Halpern


completed MD, (Harvard University)

Marianna Ruzinova


MD-PhD, Rockefeller-Sloan Kettering

Sylvia Kwakye*


Grad student, Cornell Univ

Elizabeth Glater


Post-doc, Rockefeller Univ

Jovanka Tepavcevic


Post-doc, Rockefeller Univ

Steve Vokes


Post-doc, Harvard Univ

Adisetyantari Suprapto


Regulatory affairs, Columbia Univ

Todd Kim


completed M.D.(UCLA)

Chris Chon


completed M.D.  (Stanford Univ)

Maarten Hoek


Post-doc, Cold Spring Harbor

* co-mentored by another Swarthmore faculty member

These students conducted summer research projects in my laboratory and often initiated and usually extended the projects in the academic year.  An additional 20 students spent one or two semesters in the laboratory, but took advantage of summer research experiences elsewhere.  Many students who do research in my laboratory have the opportunity to present their research at conferences and meetings.  The most prestigious meeting is the General Meeting of the American Society for Microbiology (ASM).  Poster abstracts for that meeting undergo a rigorous peer-review before acceptance.

Some of the students who have conducted summer research in my laboratory (and 2 students who were supervised by a visiting microbiology faculty member) have secured funding in the form of an Undergraduate Research Fellowship (URF) from the ASM.  Those fellows had a summer stipend, a year of student membership and travel to the ASM meeting paid by the ASM.  Their fellowships were awarded based on an application that included a personal statement, research proposal and letters from faculty members.  Competition for these fellowship is intense at the national level. 

Previous ASM URFs from Swarthmore: Meagan Bolles '06; Charlie Buffie '06; Aparna Kishor ‘05; Jeanne McFalls, ’03; Mathew So ’03; Andrew Alderete ’02; Cristina Cardemil ’01; Clarissa Nobile ’01; Nathaniel Hanson ’99 - supervised by visiting faculty member, Anna Tischler ’99 - supervised by visiting faculty member; Marianna Ruzinova ’98; Matthew Halpern ’98; Elizabeth Glater ’97; Adisetyantari Suprapto ’96

Group photos from recent students in the laboratory

The Vollmer lab hosted 2 non-science Swarthmore faculty, Cheryl Grood, Department of Mathematics and Statistics and Philip Jefferson, Department of Economics for a month in June of 2005. Together they conducted experiments in molecular microbiology and discussed communication about science to non-scientists. A poster summarizing their work was presented at a research conference at Haverford in November of 2005. The abstract for the poster (pdf)

Philip Jefferson wrote about his experience in an article in the October 6, 2005 Chronicle of Higher Education (pdf ) and also "The Economist as Biologist" in the Dec 2005 issue of the Swarthmore College Bulletin

Vollmer will host 2 more colleagues in her laboratory during the summer of 2007.

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