Harvard University - Department of Molecular & Cellular Biology


by Sophie Blum

April 22nd, 2014

There’s no such thing as a “typical” postdoc.

Sarah Anne Wacker grew up in a small Minnesotan town an hour outside Fargo, ND.
In high school, a hands-on biological research program offered Wacker an opportunity to work in the laboratory of Chris Chastain at Minnesota State University Moorhead where she explored plant enzymes involved in photosynthesis. “We were trying to figure out where a particular enzyme was located inside a plant cell,” she recalls with a smirk, “and we found that it was located in the chloroplast (which was not particularly surprising).” Nevertheless, the experience initiated a career in biological research.

Facilitated by a scholarship for undergraduates majoring in science, Wacker attended the University of Richmond in Virginia where she spent the next four years in the laboratory of Ellis Bell, investigating the allosteric regulation of metabolically-important enzymes.  While at Richmond, Wacker supplemented her B.S. in Biochemistry with a semester abroad in Copenhagen and a summer in Catherine Drennan’s lab at MIT.

After ruling out an M.D. in favor of scientific research, Wacker pursued her PhD
in chemical biology with Tarun Kapoor at Rockefeller University in New York City. As a graduate student there she developed two methods for studying interactions between small molecules and their protein targets. The first method characterized how a small molecule interacts with its known target by using crosslinking and mass spectrometry in order to better understand how a potential anti-cancer drug target is inhibited. The second method tackled the challenge of determining the physiologically relevant targets of a drug in human cells. By generating drug-resistant clones and analyzing these with high-throughput genomics technology and bioinformatics, her approach can rapidly identify the proteins to which a small molecule binds.  

While at Rockefeller, Wacker attended a talk by Rich Losick, which inspired her to consider a postdoc in his lab at Harvard University. Her background in chemical biology and protein biochemistry proved an asset to the lab’s largely genetic approach to biofilm research and she began her postdoctoral research here in August, 2012.
Not two weeks later, Wacker was hit by a car while riding her bicycle home from work. Broken bones in her neck and leg rendered her effectively bedridden for a month. Wacker marvels at Losick’s support and understanding during this period:  “He didn’t know me,” she laments, “I had been in the lab for ten days—I had gotten nothing done!” She returned to the lab in the beginning of September, conducting benchwork despite crutches with the aid of visiting fellow Tantan Gao. Within a year, she obliterated any misgivings by earning the prestigious Jane Coffin Childs fellowship for her research on bacterial communities on tomato plant roots. Remarkably, she had a completed fellowship application in her backpack at the time of the accident:

“I started yelling about it in the emergency room. That was when my husband says he knew I was okay, because for a while I had short-term memory loss and was in and out of consciousness. But suddenly I was shouting, “You have to mail that! It has to get mailed!” Then he realized, ‘Okay, she’s back to normal. Her mind is working.’”

Currently, Wacker is studying the interaction between the bacterium Bacillus subtilis and plants: “B. subtilis has been shown to protect plants from plant pathogens by colonizing plant roots and forming sessile communities, referred to as biofilms, on the roots of plants. Previous work in the Losick lab has shown that extracts of tomato roots stimulate biofilms in vitro, indicating that the plant roots produce signaling molecules that are sensed by the bacteria. The goal of my research is to identify the specific molecules from plants that are responsible for stimulating biofilm formation and to determine how they are recognized by the bacterium.” So far she has found several potential pathways through which B. subtilis can sense molecules within the plant’s extract. This project will eventually tie in to her background in small molecule-protein interactions.   

Although Bacillus subtilis has been studied extensively as a model organism bacterial biofilm research is still scarce. “We know a lot about them,” she admits, “but we don’t actually fully understand what they do in real life. We’ve just looked at one facet of their personality, you could say.” She anticipates promising agricultural applications, such as preventing plant disease and improving plant growth. Additionally, her work will contribute to a general understanding of biofilms, which may improve treatment of biofilm-associated diseases in humans.

Meanwhile, Wacker gave birth to a son, Solomon, in September of 2013. While exploring postdoctoral options, she had taken the possibility of parenthood into account, careful to consider whether advisors and universities were supportive of lab members with children and “that it wasn’t something no one had ever done before.” Juggling responsibilities is a challenge, but so far, thanks to an informal support network of postdoc parents and indispensable childcare assistance from her mother-in-law, “It’s been easier than I expected,” she offers optimistically.

While Wacker is delighted with her current occupation researching, parenting, and, this semester, teaching undergraduates, she acknowledges that the postdoc is a transient position: “As much as I enjoy what I’m doing right now, I always need to be thinking with one foot out the door because eventually I’ll need to have both feet out the door.”

After her term at MCB, Wacker intends to continue teaching and conducting research, preferably somewhere she can comfortably do both. As she points out, “You learn some things from research that you can’t learn from teaching and you learn some things from teaching that can help your research.”  At present, Wacker is leading a team of undergraduates in the Life Sciences 100r project laboratory testing bacterial isolates from China for interactions with plant roots. Rich Losick has unhesitating confidence in Wacker as an educator and testifies, “I have no doubt that she will flourish in that capacity.”

In the meantime, says Losick, “Sarah Wacker is a role model for a postdoctoral fellow who successfully combines science, teaching, and motherhood…I admire her greatly!” Wacker represents but one example of an extraordinary postdoctoral career and continues to remind us that there’s more than one definition of success in the sciences.

Find out more at PubMed.