ATP-Driven Separation of Liquid Phase Condensates in Bacteria

Area of Science:

• Cell Biology
• Molecular Biology
• Biophysics

Background:

• Liquid-liquid phase separation (LLPS) enables membrane-less compartmentalization within cells.
• The active organization and mechanisms governing LLPS condensates in subcellular space remain largely unknown.

Purpose of the Study:

• To investigate the active organization and regulation of LLPS condensates using the ParABS DNA segregation system.
• To elucidate the mechanisms underlying the formation, dynamics, and localization of these non-canonical condensates.

Main Methods:

• Characterization of ParABS system components (parS, ParB, ParA).
• Observation of condensate formation and dynamics using microscopy.
• Analysis of ParB molecule diffusion within and between condensates.

Main Results:

• ParB proteins and parS sequences form nanometer-sized, round LLPS condensates.
• ParB molecules exhibit rapid diffusion within the nucleoid but confined motion within condensates.
• ParA motor protein is essential for preventing ParB condensate fusion.
• Nucleation of condensates is strongly promoted by parS.

Conclusions:

• The ParABS system utilizes an active mechanism for organizing non-canonical LLPS condensates.
• This mechanism involves ParA-mediated prevention of condensate fusion, facilitating splitting, segregation, and localization.
• LLPS condensates can be actively and specifically organized in subcellular space without membranes.