The Bacillus subtilis division protein DivIC is a highly abundant membrane-bound protein that localizes to the division site

The Bacillus subtilis divIC gene is involved in the initiation of cell division. It encodes a 14.7 kDa protein, with a potential transmembrane region near the N-terminus. In this paper, we show that DivIC is associated with the cell membrane and, in conjunction with previously published sequence data, conclude that it is oriented such that its small N-terminus is within the cytoplasm and its larger C-terminus is external to the cytoplasm. DivIC is shown to be a highly abundant division protein, present at approximately 50 000 molecules per cell. Using immunofluorescence microscopy, DivIC was seen to localize at the division site of rapidly dividing cells between well-segregated nucleoids. Various DivIC immunostaining patterns were observed, and these correlated with different cell lengths, suggesting that the DivIC localization takes on various forms during the cell cycle. The DivIC immunolocalization patterns are very similar to those of another membrane-bound B . subtilis division protein, DivIB.