Study of the mechanical properties of bacterial cells will be pursued using textile fiber techniques on the amplifying Bacillus subtilis system: thread and macrofibers. The long term goal is to understand the forces acting during cell growth and division, in particular the role forces play in determination and maintenance of cell shape, and ultimately how cells may use information about their physical state in regulation. Particular attention will be given to the mechanical properties of cell walls in thread with respect to anisotropy and visco-elasticity by measurement of stress-strain relationships (tension versus extension, torque versus twist, and torque versus extension). The molecular structure of the cell wall responsible for the material properties will be explored by treating the specimens in ways known to modify the wall and by exposing specimens to environments that change the physical state of wall polymers in known ways. Mechanical properties of microfibers will be sought in order to infer the material properties of the cell wall in vivo. The effects of mechanical stress on growth and viability will be determined by examination of specimen recovery after varying degrees of deformation and by study of growth under tension or blocked rotation. The properties observed will be used to predict wall deformation during growth involving both upwelling and extension processes, and to describe the mechanical components of cell shape determination and maintenance. An attempt will be made in conjunction with ultrastructure studies (done by others) to produce a molecular model of the organization of cell wall polymers on the cell surfaces. The project is related to health at two levels: first it will provide new fundamental information about cellular biomechanics pertinent to a broad range of biological processes, and secondly, it will provide new information about bacterial cells and their surfaces that may pertain to the interactions between bacterial and mammalian cells, or bacteria and anti-bacterial agents. cells, or bacteria and anti-bacterial agents.
