Peptidoglycan polymerase that is essential for cell division. [GlcNAc-(1->4)-Mur2Ac(oyl-L-Ala-gamma-D-Glu-L-Lys-D-Ala-D-Ala)](n)-di-trans,octa-cis-undecaprenyl diphosphate + beta-D-GlcNAc-(1->4)-Mur2Ac(oyl-L-Ala-gamma-D-Glu-L-Lys-D-Ala-D-Ala)-di-trans,octa-cis-undecaprenyl diphosphate = [GlcNAc-(1->4)-Mur2Ac(oyl-L-Ala-gamma-D-Glu-L-Lys-D-Ala-D-Ala)](n+1)-di-trans-octa-cis-undecaprenyl diphosphate + di-trans,octa-cis-undecaprenyl diphosphate + H(+) Cell wall biogenesis; peptidoglycan biosynthesis. Forms a complex with FtsZ and PbpB (PBP3, FtsI). Localizes to the division septum. Interacts with FtsZ via its C-terminal region, and with PbpB via two extracytoplasmic loops. Belongs to the SEDS family. FtsW subfamily.