A non-essential division protein that localizes to the septal ring in low ionic strength medium. Localizes to the septal ring in about 30% of observed cells before cell constriction occurs; localization occurs in low ionic strength medium (0 NaCl) and requires FtsZ but not FtsEX. Overexpression partially restores correct FtsI localization to the division septum in an ftsEX deletion. Isolated as a multicopy suppressor of an ftsEX deletion mutant; it does not suppress other cell division defects (e.g. ftsA, ftsI, ftsQ or ftsZ). Bacterial adenylate cyclase hybrid (BACTH) studies show interaction of this protein with DamX, FtsI, FtsN, FtsQ, YmgF, DedD, FtsA and MalF, as well as weaker interactions with DedD, MalG and PBP2, but this assay often generates false positive results. Localizes to the septal ring before constriction, only when cells are grown at low ionic strength. Constitutively expressed at low levels in mid log phase, in high (10 g/ml NaCl) and low (0 g/ml NaCl) ionic strength medium (at protein level). No visible phenotype in rich, rich without NaCl or minimal medium. Double dedD-drpB deletion mutants grow 1000-fold less well at 42 degrees Celsius and are filamentous when grown on LB, no effect is seen in low ionic strength medium; few septa are observed. Belongs to the DrpB family. Extended N-terminus. Extended N-terminus.