Forms membrane-associated dynamic filaments that are essential for cell shape determination (PubMed:11290328, PubMed:15745453, PubMed:17064365, PubMed:19117023, PubMed:19659933). Acts by regulating cell wall synthesis and cell elongation, and thus cell shape (PubMed:19659933). A feedback loop between cell geometry and MreB localization may maintain elongated cell shape by targeting cell wall growth to regions of negative cell wall curvature (By similarity). Filaments rotate around the cell circumference in concert with the cell wall synthesis enzymes. The process is driven by the cell wall synthesis machinery and does not depend on MreB polymerization (PubMed:21636745, PubMed:21636744). The active movement of the MreB cytoskeleton stimulates diffusion of membrane proteins (PubMed:24603761). Organizes peptidoglycan synthesis in the lateral cell wall (PubMed:19659933). Also required for proper chromosome segregation (PubMed:14588250, PubMed:15745453, PubMed:17064365). Membrane fluidity influences MreB movement; in rich medium MreB movement is significantly decreased in a floA-floT mutant (PubMed:32662773). Polymerizes in the presence of millimolar divalent cations in a protein concentration-dependent manner. Polymerization is favored by decreasing pH and inhibited by monovalent salts and low temperatures. Forms polymers (PubMed:11290328, PubMed:15745453, PubMed:17064365, PubMed:19117023). Forms a complex with Mbl and MreBH (PubMed:17064365, PubMed:19659933). Membrane-associated (PubMed:15745453, PubMed:17064365). Localizes in the form of helical filaments that encircle the cell (PubMed:11290328, PubMed:15745453). Localization is affected by Mbl, MreBH, MreC and MreD (PubMed:15745453). Colocalizes with MreBH and Mbl (PubMed:16950129, PubMed:17064365). Disruption of the gene results in loss of cell width control (PubMed:11290328). Depletion leads to a strong defect in chromosome segregation (PubMed:14588250, PubMed:15745453). It also leads to the formation of enlarged cells, to the loss of mid cell localization of the replication machinery and to growth arrest (PubMed:15745453). Double dynA-mreB deletions have strong cell shape defects (PubMed:23249255). B.subtilis has three MreB paralogs: MreB, Mbl and MreBH. All paralogs have the ability to support rod-shaped cell growth normal conditions. The multiplicity of paralogs becomes important under stress conditions. They are probably used to allow cells to maintain proper growth and morphogenesis under changing conditions. Belongs to the FtsA/MreB family.