OCISB Seminar: Evolution and regulation of bacterial growth, morphology, and development

The diversity of shapes of organisms is one of the most fascinating aspects in the field of biology. The seminar will focus on the mechanisms of cell growth and morphological change in the alphaproteobacteria. Many bacteria belonging to the Caulobacteraceae family (including Caulobacter, Asticcacaulis, Brevundimonas, and Phenylobacterium) share a sub-cellular organelle named the stalk, which is a true extension of the cell body comprised of all layers of the cell envelope. Stalk synthesis represents a precisely localized morphological transformation. The number as well as the position of stalks can vary among different species within the group. I will describe a protein that plays a critical role in the positioning of stalks and discuss how its evolution leads to different stalk positioning and number in different species. In the second part of the talk, I will show how evolutionary consideration of the mechanism of budding, in which cells grow from the tip of their stalks, led to a surprising discovery about growth mechanisms. I will show that polar growth, rather then the assumed binary fission, is the predominant mode of growth in a large group of the alphaproteobacteria that includes the plant pathogen Agrobacterium tumefaciens and the human pathogen Brucella abortus. Finally, I will describe new methods of peptidoglycan labeling that allow the labeling the sites of active peptidoglycan synthesis in live cells and in real time.