Date & Location: April 10, 2023, at 4p
Location: PBL 247
Meeting ID: 959 9631 3892
Subject: Yes! Bacteria have organelles! How are they organized?
Host: Danny Ducat
About the Speaker
Institution: University of Michigan
Abstract: Bacteria have a diversity of organelles involved in essentially all aspects of cell function. Yet, the mechanisms governing organelle assembly, organization, and homeostasis remain largely unstudied in bacteria. The cytoskeleton and motor proteins are well known for organizing the membrane-bound organelles of eukaryotes. But bacteria lack extensive membrane-bound organelles, cytoskeletal structures, and linear motors. Instead, bacterial organelles are largely protein-based and a widespread family of proteins, called ParA/MinD (A/D) ATPases, are responsible for their subcellular organization, but the mechanisms remain unclear. My lab is focused on the molecular mechanisms underlying the subcellular organization of bacterial organelles, of which I will discuss 3 research vignettes. (1) Our focus so far has been on a carbon-fixing icosahedral organelle called the carboxysome. Carboxysomes encapsulate the most abundant enzyme on Earth, Rubisco, within a selectively permeable protein shell to create the high CO2 environment needed for efficient CO2 fixation. Carboxysomes are responsible for almost half of global CO2 fixation, and are therefore of great ecological and biotechnological interest; especially in the face of our climate crisis. The bulk of our work has been centered on the carboxysome positioning system. (2) While performing this work, several recent studies found that carboxysomes and several other bacterial organelles behave as liquids. The carboxysome, and its positioning system we identified with the Ducat group, represent a tractable model for understanding the spatial regulation of liquid-like organelles. We are interested in determining the role of material state in organelle assembly, function, and organization in the cell. (3) Finally, the list of A/D ATPases that spatially organize bacterial organelles is growing. We found that a third of sequenced bacteria encode multiple A/D ATPases, each of which positions a specific cellular cargo. Yet, how A/D ATPases coordinate their positioning reactions in the same cell has never been studied. The final project I will discuss focuses on understanding how organelle trafficking reactions are coordinated with each other, with DNA segregation and with cell division. Overall, our work thus far has uncovered unknown, unique molecular mechanisms of positioning and confinement in the cell.