from Bacillus: Cellular and Molecular Biology Peter Graumann University of Freiburg, Germany

Bacillus subtilis is one of the best understood prokaryotes in terms of molecular biology and cell biology. Its superb genetic amenability and relatively large size have provided powerful tools to investigate a bacterium in all possible aspects. Recent improvements in fluorescence microscopy-techniques have provided novel and amazing insight into the dynamic structure of a single cell organism. Research on B. subtilis has been at the forefront of bacterial molecular biology and cytology, and the organism is a model for differentiation, gene/protein regulation and cell cycle events in bacteria.

Bacillus subtilis is a ubiquitous soil bacterium that can be easily isolated from soil, using starch as an energy source and relatively high salt concentration. Ideally, the soil sample is heated up to 100°C for 30 minutes, allowing only for enduring spores to be cultured from the sample. B. subtilis is unique in that it can choose between at least 3 different genetic programs when nutrients or other resources become scarce, and/or cell density reaches a critical threshold. To survive or adapt to adverse condition, cells can either enter stationary phase, which is characterized by the formation of single motile cells (exponentially growing cells usually grow in chains and are non-motile), differentiate into enduring and metabolically inactive spores, or become competent and take up DNA from the environment for acquisition of new genetic material. In all three cases, strikingly different genetic programs are turned on that guide the cell through the differentiation processes. In addition to this, B. subtilis shows social behaviour, in that the cells communicate with each other, and form multicellular structures in the form of swarming cells and biofilms. Two component systems, cascades of different sigma factors, regulatory RNAs and specific proteolysis of target proteins form an intricate regulatory network, which is beginning to be unravelled, not only in terms of specific processes, but also in terms of whole complex processes that are connected with each other. Most strikingly, it has become clear that many proteins have specific subcellular addresses in bacterial cells. These findings have established the field of "Bacterial Cell Biology", and B. subtilis has been a forerunner in this field. Many vital processes are disturbed if proteins lose their specific localization, but the fundamental question of how proteins are targeted and specifically located in a call lacking intracellular compartments is still unclear for most cases. Therefore, it has become important to also study proteins in terms of their localization within the cell, in addition to analysing their biochemistry and regulation. It is important to understand how a bacterial cell functions as a whole entity and in 3D, i.e. how it is spatially organized, and even how bacteria talk to each other, or give their life for the sake of the whole community.


Further Information: Bacillus: Cellular and Molecular Biology