Research

The idea of a bacterial cell as a disorganized sack is obsolete. We now know that bacteria have a diversity of organelles involved in essentially all aspects of cell function. Yet, the mechanisms governing organelle assembly, organization, and homeostasis remain unknown and virtually 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. The goal of my lab is to determine the molecular mechanisms underlying the subcellular organization of bacterial organelles.

Focus I – Organelle Trafficking & Homeostasis

Bacteria make waves to position their organelles.
We are trying to understand how.

Carboxysomes encapsulate the most abundant enzyme on Earth, Rubisco, within a selectively permeable 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 & biotechnological interest; especially in the face of our climate crisis. In Focus I we ask: How are carboxysomes spatially regulated in the cell?

Focus II – The Material State of Bacterial Organelles

Compartmentalization is a key feature in cell function for all life. In eukaryotic cells, this is classically achieved via membrane-bound organelles (left). But over the past decade, “membraneless” compartments (right) have emerged – biocondensates with material properties distinct from the surrounding dilute phase. In Focus II we ask: Do biocondensates also form & compartmentalize reactions in bacteria?

Focus III – Coordinated Organelle Trafficking in Bacteria

ParA/MinD ATPases spatially organize an array of cellular cargos. Yet, it remains unknown how multiple A/D ATPases can coordinate the positioning of such a diverse set of fundamental cargos in the same cell. We recently found that a third of bacteria encode multiple A/D ATPases (see left). Among these bacteria, we identified several human pathogens as well as the experimentally tractable organism, Halothiobacillus neapolitanus, which encodes seven A/D ATPases. We directly demonstrate that five of these A/D ATPases are each dedicated to the spatial regulation of a single cellular cargo: the chromosome, the divisome, the carboxysome, the flagellum, and the chemotaxis cluster. In Focus III, we use H. neapolitanus to ask: How is organelle trafficking coordinated with the bacterial cell cycle?

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