Research

As a postdoc in Pam Silver’s group in the Systems Biology Department at HMS, I’m exploring various aspects of intracellular organization in bacteria, focusing on naturally and synthetically generated compartments.

AlfA actively segregates plasmids in B. subtilis

AlfA actively segregates plasmids in B. subtilis

Justin Kollman's helical reconstruction of an AlfA filament over a background of negatively-stained bundles.

Justin Kollman’s helical reconstruction of an AlfA filament over a background of negatively-stained bundles.

During my PhD at UCSF with Dyche Mullins, I characterized a three component system that uses an actin homolog to actively segregate plasmids in B. subtilis. First, we characterized the assembly properties of the filament, showing that AlfA assembles into highly-twisted filaments that spontaneously self-associate into bundles. Next, we discovered the regulatory mechanisms of the accessory factor, AlfB, and reconstituted DNA segregation in vitro. Briefly, we found that AlfB alone disrupts filament assembly and stability, preventing formation of bundles and raising the critical concentration for assembly. However, when assembled onto a centromere-like piece of plasmid DNA, parN, AlfB forms a complex that can bind to the ends of AlfA filaments. In this form, AlfB instead promotes filament assembly: lowering the critical concentration and rescuing bundling. The polymerization of these filaments propels the plasmids bound at their ends; when two AlfB/parN-bound filaments bundle together, they segregate DNA by pushing it in opposite directions. (F1000 review of this work.)

As an undergrad at UNC-CH, I had the fortune of working with Ted Salmon’s group on the Ndc80 complex and the kinetochore.