The dynamic nature of the bacterial cytoskeleton

Abstract

Three of the four well-established bacterial cytoskeletal systems-the MreB, MinCDE, and FtsZ systems-undergo a variety of short-range and long-range dynamic behaviors. These include the cellular reorganization of the cytoskeletal elements, in which the proteins redistribute from a predominantly helical pole-to-pole pattern into annular structures near midcell. Despite their apparent similarity, these dramatic redistributional events in the three systems are in large part independent of each other. In addition, some of the cytoskeletal structures undergo oscillatory behavior in which the helical elements move repetitively back-and-forth between the two ends of the cell. The details and mechanisms underlying these dynamic cellular events are just now being revealed by fluorescence microscopy of intact cells, fluorescence photobleaching recovery studies, single molecule tracking techniques, and in vitro studies of the purified proteins.

Fig. 1

Dynamic behavior of MinCDE system. a Fluorescence micrograph of Yfp-MinD showing coiled helical structure extending along the cell cylinder with high concentration of Yfp-MinD in coils at one end of the cell (“polar zone”). b Distribution of MinDE at different stages of an oscillation cycle. Blue lines represent MinDE coiled structures within the polar zones (solid line) and extending to the opposite pole (dashed line). Red line represents MinE ring. (Reprinted from [15], with permission of the publisher)

Fig. 2

Yfp-MreB helical cytoskeleton (a) and cytoskeletal doublet rings (b). The progressive movement apart of the rings is shown in panels b–d. (Reprinted from [44], with permission of the publisher)

Fig. 3

Division and segregation of the MreB cytoskeleton during the E. coli cell cycle (a) and proposed model for the role of the cytoskeletal rings in the interruption and resealing of the MreB cytoskeletal helices that leads to duplication of the MreB helical structure (b). MreB in blue, FtsZ in red. (Reprinted from [44], with permission of the publisher)

Fig. 4

Two-dimensional images of FtsZ structures in B. subtilis cells stained with anti-FtsZ antibody. a Cell with an FtsZ helix, but no Z ring. b Cell with a Z-ring and FtsZ helix. A cartoon for each cell is shown depicting the interpreted location of FtsZ within the cell. (Reprinted from [57], with permission of the publisher)