Bacterial Cell Division: Mechanisms and Regulation.

Abstracts are not currently available in GtR for all funded research. This is normally because the abstract was not required at the time of proposal submission, but may be because it included sensitive information such as personal details.

Cell division is a fundamental process common to all living organisms. However, in no system is the process understood in molecular detail. This proposal describes a major programme aimed at trying to understand several aspects of cell division in a relatively simple organism, the bacterium Bacillus subtilis. This is an extremely tractable experimental system and one in which there is some prospect of understanding in molecular detail on a reasonable time scale. Division is governed by a tubulin homologue FtsZ which assembles into a ring-like structure at the site of impending division. About 10 other proteins associate with the ring to regulate its formation and help bring about constriction of the cell and synthesis of new cell wall and membrane. This proposal describes a 5 year program of research aimed at improving our understanding of various components of the division machinery. The proposal is divided into three themes. The first part concerns the early, cytosolic proteins involved in division, centred on FtsZ. We want to identify any remaining proteins involved in interactions with FtsZ and to define the network of interactions, with particular reference to the surface of FtsZ. We will use information on the network of interactions to facilitate biochemical reconstruction of the Z ring in vitro. If possible, we will try to exploit advances in imaging technology to improve our resolution of the structure of the Z ring in vivo. The second part concerns detailed characterisation of a new protein we have found that plays a key part in positioning the Z ring relative to the bacterial chromosome. It is responsible for a well-known effect in bacteria called nucleoid occlusion. The protein, Noc, will be analysed genetically and biochemically. It appears to have two separable functions: binding to the chromosome, and inhibition of the division machinery. We will try to reconstitute and characterise these activities in vitro. Finally, we will examine the role of this protein in a round pathogenic bacterium, Staphylococcus aureus (as opposed to the rod-shaped B. subtilis). The third theme concerns the late events of cell division, involving a set of transmembrane proteins required for synthesis of cell wall material in the division septum and possibly the membrane dynamics associated with division. We will characterise the last remaining protein of this group, FtsW and test its possible involvement in cell wall precursor synthesis. We will then investigate how the key player in cell wall synthesis during division, PBP 2B, is positioned and regulated by the FtsL, DivlB, DivlC and possibly FtsW proteins. We will then try to characterise the other facet of PBP 2B function by identifying the proteins that it interacts with to bring about wall synthesis. Finally, we will test the possible roles of the FtsL and DivlC proteins in membrane dynamics. Ultimately, this work should lead to a more complete understanding of the set of proteins responsible for cell division in B. subtilis and related bacteria. It should also take us some way towards reconstructing some of the key events of cell division in the test tube.