Bacteria are the most populous and variable form of life on Earth. Bacteria can cause disease in humans as well as in animals and plants important to the food supply and the environment. However, bacteria can also be beneficial (probiotics) and are used industrially in the production of pharmaceuticals. Controlling bacterial populations is necessary to prevent disease and for quality control in industrial settings. Antibiotics are used to kill bacteria, but the development of new antibiotics has not kept up with needs in medicine and industry. Most antibiotics kill bacteria by causing mechanical failure (rupture) of the cell wall leading to cell death. The research goal of this work is to determine how bacterial physiology changes in response to physical forces and to determine how well the bacterial cell wall resists physical forces. The educational objectives of the work are to lead a week-long workshop on the mechanical properties of biological materials targeted to high-school students from traditionally under-represented groups and contribute to other activities to broaden participation in science by members of under-represented groups within the institution and at the national level.
Two hypotheses have been presented to explain the location and migration of intracellular proteins involved in cell wall synthesis: a) intracellular proteins involved in cell wall synthesis are directed by local cell wall curvature; and b) that cell wall synthesis proteins are directed to locations of increased cell wall stress/strain. This work addresses this question using a microfluidics-based mechanical testing approach that can modify mechanical stress/strain without large changes in cell wall curvature. The approach is novel in that it makes it possible to observe intracellular proteins in live bacteria while mechanical loading is being applied and does not require conditions of altered bacterial physiology (altered osmolality, filamentous growth, etc.). The research goals of this work are to: 1) Determine the relationship between mechanical strain, regions of cell wall growth and subcellular movement of a protein associated with cell wall synthesis (the MreB protein); and 2) Determine the entire mechanical strain field in the bacterial cell wall while load is applied.
