Membrane Partitioning by and for Cell Wall Synthesis
Diffuse, sidewall patterning of cell wall peptidoglycan synthesis by the actin homolog MreB enables model organisms like Escherichia coli and Bacillus subtilis to maintain rod shape. Mycobacteria are also rods but grow from their poles and lack MreB. It is unclear how mycobacteria establish and propagate rod morphology. My lab has investigated the roles of the essential, cytoskeletal-like protein DivIVA (Wag31) and of inner membrane partitioning in polar growth and envelope assembly. Our work with the model organism M. smegmatis suggests that the membrane-cell wall axis is a self-organizing system in which DivIVA-directed cell wall synthesis organizes the inner membrane, and an organized inner membrane in turn makes cell wall synthesis more efficient and precise. These findings complement what has been reported for eukaryotic cell membranes, which can be partitioned by pinning to cytoplasmic structures such as the actin cytoskeleton and to external structures like extracellular matrix and cellulose. They are also congruent with the literature on model lipid bilayers, which can be phase separated by adhesive forces.