Essential cell division protein that may play a structural role. Probably involved in the regulation of the timing of cell division. Also required for sporulation. Monomer. Interacts with DivIB and DivIC. Interaction with DivIC stabilizes FtsL against RasP cleavage. Localizes to the division septum where it forms a ring structure. Remains localized at mid-cell during the whole septation process. Localization requires FtsZ, DivIB, DivIC and PBP-2B. Transcribed at a low constant level in all growth phases. Part of the mraZ-rsmH-ftsL-pbpB operon. The cytoplasmic region is involved in protein stability. Cleaved by RasP. Cleavage is important for turnover and function of FtsL. Essential, it cannot be deleted. Is thermodynamically highly unstable and is likely to be rapidly degraded unless stabilized by interaction with other septasomal proteins. Belongs to the FtsL family. The question of whether FtsL and DivIC interact directly (PubMed:16936019) or indirectly (PubMed:11994149) remains controversial.