Aretha Fiebig

###Education
B.A., 1996, Earlham College
M.S., 1999, University of Chicago
Ph.D., 2003, University of Chicago
Postdoctoral Fellow, 2003-2005, Stanford University

###Research
My work centers on understanding how microorganisms sense and respond to their environment, which is important in maintaining homeostasis and optimizing fitness. I primarily employ genetic approaches to probe the function of environmental sensory systems with a particular focus on regulation of bacterial surface attachment and bacterial stress responses.  

Alphaproteobacteria are a diverse class of microbes that inhabit a wide range of environmental niches and include free living and host-associated symbionts and pathogens.  Within this class, I study organisms adapted to habitats including freshwater, marine and soil ecosystems, and the interior of mammalian cells.  

Regulation of surface attachment
In the environment, bacteria primarily inhabit surfaces.  Genetic systems that control development of features that enable a surface-attached lifestyle are critical for bacterial fitness, and are regulated largely by signals from the environment.  Many Alphaproteobacterial species utilize a polar adhesin, often called a holdfast, to attach to solid substrates and air-liquid interfaces.  My work on the freshwater and soil bacterium, Caulobacter crescentus, has revealed a potent small protein regulator, HfiA, that governs synthesis of this adhesin.  Current work is aimed at understanding how environmental signals tune HfiA expression and how diverse signals are integrated by the bacterial cell to affect holdfast synthesis. 

Stress responses
Within the Alphaproteobacteria, the core molecular components of the general stress response signaling system are conserved.  However, the sensory proteins that activate this environmental response system vary widely in number and in the signals they detect, even between closely related species.  I am investigating how genetically encoded differences in these sensory proteins intersect with environmental signals to influence the physiology of different microorganisms.