Joel Kralj

Scholar: 2015

Awarded Institution
Assistant Professor
University of Colorado
Department of Molecular Cellular and Developmental Biology


Research Interests

Deciphering Bacterial Electrophysiology


Every living cell maintains a voltage relative to the outside world. Evolution has harnessed cellular voltage changes in numerous ways including information transfer in neurons, mechanical contraction in muscle, and energy generation in mitochondria. Moreover, voltage misregulation is coupled to diseases as varied as cancer, heart failure, and autoimmunity. The scope of voltage dynamics in nature highlights the crucial role it plays in maintaining life.

Electrical signaling in bacteria, which are too small to measure with wires, has largely been ignored due to our inability to record from live cells. However, in 2011 we discovered a fluorescent protein that converts electrical changes to optical changes, allowing us to record voltage simply by taking a movie. We used this protein to uncover bacterial voltage transients on the second time scale, similar to neurons and cardiomyocytes in mammals. This finding launched the field of bacterial electrophysiology and revolutionized our understanding of the evolutionary origins of electrical signaling. My lab is focused on understanding how and why bacteria rapidly modulate voltage.

We are currently working to discover the genes and small molecules that generate and modulate voltage in lab strains of E. coli. We are also exploring how bacteria use electrical transients to adapt to noxious external stimuli including antibiotics and other chemical insults. We expect our results will help uncover novel strategies used by bacteria to cope with changing environments, and reveal new countermeasures we can deploy to control bacterial growth.

Another facet of our research centers on the role of bacterial voltage during human infection. We are using pathogenic strains of bacteria to record voltage in their planktonic state, during cell adhesion, and throughout endocytosis and replication in a host epithelial cell. Ultimately, we hope to generate a microfluidic representation of the human gut to monitor populations of pathogenic strains in a sea of commensal bacteria to understand how multiple species of bacteria all interact with the gut lumen.