Dirk-Jan Scheffers

Pathogenic bacteria that are resistant to most or all classes of existing antibiotics are rapidly emerging and are the cause of many problematic infections in hospitals. Notorious examples include Methicillin Resistant Staphylococcus aureus (MRSA), multi-drug resistant Mycobacterium tuberculosis and Acinetobacter baumannii. Alarmingly, nearly all antibiotics currently in the drug development pipelines are variations on old themes, making it likely that multidrug resistant bacteria will readily acquire resistance against these not-so-novel drugs. Therefore there is an urgent need for new drug targets. In this respect, bacterial cell division is one of the most promising targets for the development of new antibacterial drugs. We are exploring cell division as a target to combat a plant pathogen - Xanthomonas citri subsp citri - that infects citrus trees. This work we do in collaboration with Dr. Henrique Ferreira, from Rio Claro, Brazil. In order to gain more insight into bacterial cell division, we study fundamental aspects of division in two well characterized model bacteria. Cell division appears simple, with a bacterium growing, splitting through the middle after which the two bacteria start growing again. Simple as it may seem, this division process involves the coordinated action of a large number of proteins that ensure that division occurs at exactly the right time and place, the middle of the cell. Cell division starts with the formation of a ring composed of protein filaments of FtsZ, just underneath the membrane. This ring organizes all other proteins that play a role in division. Since many of the individual division proteins interact and localize to the ring, they are proposed to form a large multi-protein machinery, called the divisome. How the divisome works on a molecular level is poorly understood as the analysis of the divisome is complicated by the fact that most of its components are membrane proteins. Our work addresses three fundamental questions about bacterial division. First, how is the formation of FtsZ filaments regulated by accessory proteins to ensure that the FtsZ ring is formed at the right time and place? Second, does the divisome exist and if so what is its composition? Third, how does the organization of cell division proteins in complex(es) work to aid division? To answer these questions, we are using a set of biochemical techniques including native gel electrophoresis, immunoprecipitation and advanced microscopy. The goal of our work is to generate important novel insights in how bacteria regulate their replication.