A dynA ezrA double deletion leads to a strongly exacerbated phenotype in cell division, suggesting that like EzrA, a regulator

of FtsZ ring formation, B. subtilis dynamin affects an early stage in cell division. However, the combination of a dynA deletion with a divIB deletion also leads to a synthetic effect on cell division. DivIB affects a state in division clearly later than the formation of the Z ring, indicating that the function of DynA in division cannot be correlated with a defined stage in division. In any event, the accumulation of dynamin at the Z ring underlines the idea that dynamin confers a function during division. Expression of DynA in a eukaryotic cell system showed that the protein has intrinsic affinity to the cell membrane Fer-1 in vitro and can assemble into tubulated PKC412 chemical structure structures. However,

these pointed outwards of the cells, while the assumed function of dynamin in the bacterial cell would either be an inward bending of the membrane during cell division, or the fusion of membranes as the last step during division. It is likely that DynA needs cofactors for its appropriate function in the bacterium. Interestingly, the combination of a dynA deletion with the deletion of a gene encoding for a flotillin-like protein, FloT, also leads to a synthetic defect in cell division. Flotillin proteins are implicated in lipid raft formation in eukaryotic and in prokaryotic cells. Although our experiments do not allow Pyruvate dehydrogenase us to make any clear conclusion as to the detailed function of dynamin or flotillin, they show that bacterial dynamin and flotillin proteins play non-redundant functions in membrane dynamics. This is supported

by our findings that each mutation does not affect the localization of the other protein. We suggest that dynamin is see more important for the generation of cell curvature, possibly via its putative mechanochemical activity, and likewise flotillin proteins, which may be important to recruit lipids that favour membrane bending. Indeed, there appears to be a link between flotillin in B. subtilis and membrane fluidity [37]. This idea is supported by our finding that DynA can distort the cell membrane in a heterologous cell system, suggesting that DynA may facilitate membrane invagination and/or couple Z-ring formation with membrane invagination. Alternatively, flotillin may be important to facilitate the recruitment of cell division proteins to the Z ring. In any event, the role of dynamin and flotillins in cell division is not redundant, because of the synthetic effect, and because of their different localization patterns.