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Postdoctoral opportunities in the Physics of Biological Systems. OCTOBER 15 DEADLINE.

10/8/2019 4:36:41 PM

 

Dear students, 
 
We are in the midst of our annual search for postdoctoral fellows, both theorists and experimentalists, interested in the physics of biological systems.  
 
Our efforts at building an interactive and collaborative environment have been invigorated by the establishment of the Center for the Physics of Biological Function, https://biophysics.princeton.edu, a joint effort between Princeton University and The Graduate Center of the City University of New York.  We are a group of fourteen faculty working on problems across the full range of biological organization, from single molecules to groups of organisms, united by our search for common physical principles underlying the beautiful phenomena of life.
 
Center Fellows are an essential part of our intellectual community, and will have the flexibility to initiate and pursue projects that span the interests of multiple faculty mentors.  We have a particularly strong culture of theory/experiment collaboration, and individual Fellows often have played key roles in developing these collaborations.  Successful fellows have come both from PhDs in biological physics and from more traditional areas of physics; some have had as many as four different faculty co-authors during their time with us, while some have written papers only with other postdocs and students. 
 
Applications must  be made via https://puwebp.princeton.edu/AcadHire/apply/application.xhtml?listingId=12904.  We plan to start reading applications by 15 October, and interview a first group of candidates on 18-19 November, so we hope that interested candidates will act soon.  Start dates as early as February 2020 are possible, and we expect all new Fellows to join us by Fall 2020.
 
In addition to the Center Fellow position, candidates interested in combining research with a modest amount of teaching should consider applying to the new Lewis-Sigler Scholars program at Princeton, which again is looking for both theorists and experimentalists https://puwebp.princeton.edu/AcadHire/apply/application.xhtml?listingId=13061
 
Information for postdoctoral fellowships at the Princeton Center for the Theoretical Sciences could be found here, https://puwebp.princeton.edu/AcadHire/nominations/index.xhtml?listingId=12881
 
William Bialek and Joshua Shaevitz
Directors, Center for the Physics of Biological Function

2/14/2014

Escherichia coli, a rod-shaped bacterium commonly found in the lower intestines of humans and other warm-blooded animals, varies widely in the number of flagella on the surface of any individual bacterial cell. Flagella—rotating whip-like structures driven by reversible motors— rotate in a counterclockwise direction to propel the bacterial cell in a swimming motion called “running”. When at least one flagellum moves in a clockwise direction, the cell begins to “tumble”, changing its directional course.

E. coli is able to control the time it spends swimming or tumbling to move towards a nutrient, such as glucose, or away from certain harmful chemicals. However, the details of how the number of flagella and the direction of rotation—clockwise or counterclockwise—influence the motion of the bacterium are not fully understood.

Yann Chemla
Yann Chemla

Now a research team led by biological physicists Yann Chemla at the University of Illinois and Ido Golding at Baylor College of Medicine has experimentally demonstrated that individual flagella on the same E. coli cell tend to move in a coordinated way, whether swimming or tumbling. The team used “optical tweezers” to immobilize individual E. coli cells under a microscope, enabling for the first time simultaneous tracking of both swimming behavior and flagellar motion for long durations.

Tumbling, the team observed, could be caused by a single flagellum stopping a run, but it often involves a concerted effort by many of the cell’s flagella. Based on their observation that E. coli cells with more flagella spend less time tumbling than would be predicted if a single flagella always “vetoed” a run, the team proposes a new mathematical relationship between the number of flagella on the cell, the direction of rotation, and the resulting probability that the cell will tumble.

This work shows that swimming behavior in bacteria is less affected by variations in the number of flagella than expected.

Chemla explains, “What we’ve found is that E. coli has developed a mechanism that makes it relatively insensitive to variations in flagellar number. A cell will run and tumble about the same regardless of how many flagella it has—which is a good thing. Otherwise cells with few flagella would run too much, and cells with many flagella would tumble too much.”

This phenomenon may provide evolutionary advantages to E. coli.

“These cells need to be swimming and tumbling at an optimal frequency to survive,” continues Chemla. “If it runs too much, it can move away from areas with lots of nutrients or toward areas that may be toxic with no mechanism to get out. If it tumbles too much, it can never go anywhere and can get stuck in a bad spot.”

In continuing research, the team plans to explore further the mechanism by which bacteria coordinate their flagella.

In the laboratory, E. coli chemotaxis—locomotion prompted by the presence of particular chemicals in the cell’s environment— is considered a model system for studying cellular decision-making. The signaling network inside the cell that causes it to run and tumble has been studied extensively, but it hasn’t been correlated directly to the cell’s swimming behavior.

“Understanding how the cells process information from their environment to pick alternate fates—like swimming vs. tumbling—is certainly a goal. How this decision-making feature evolved in a simple organism like E. coli could provide insights into decision-making in more complex organisms,” asserts Chemla.

The team's findings have been published in the online journal eLIFE.

link to article: elife.elifesciences.org/lookup/doi/10.7554/elife.01916