In natural settings, bacteria organize themselves in multicellular communal structures known as biofilms, rather than existing in free flowing or planktonic states. A key feature of biofilms is the ability of the constituent bacteria, which are genetically identical, to exhibit a range of phenotypes according to a variety of specific and non-specific cues. The spatiotemporal variations in the expression of these different phenotypes (swimming, matrix production, and sporulation) and how the biofilm regulates these behaviours across millions of individual members is the focus of my research. Previous work in our group has shown that in addition to biochemical signals which trigger transitions from e.g. swimming to matrix production, the bacteria can also sense physical changes in osmotic pressure (see http://labs.mcb.harvard.edu/Losick/pdf/311%20-%20Rubinstein%20-%20Osmotic%202012.pdf). Using bacillus subtilis as the model organism and confocal microscopy as the tool, I want to answer a number of existential questions surrounding the production of bacterial slime: 1) How does a bacteria decide what it should do with its life, 2) how does it know how old it is and where it is, and 3) how do they decide who are their friends and who are their enemies. The results of this work could provide insight into how to control biofilm formation and provide new ways to tackle the deadly diseases associated with biofilm infections or alternatively provide ways to harness bacteria to produce clean energy.