This report discusses an experiment that was done to demonstrate the effects of lysozyme on populations of Gram positive and Gram negative bacteria. Bacteria have a cell wall composed of peptidoglycan that gives the wall its strength. Gram negative bacteria have and extra component of lipopolysaccharide (LPS), that is stabilized with magnesium ions, to their cell wall that further protects them. When Gram positive bacteria are treated with lysozyme, the lysozyme breaks down the peptidoglycan, allowing the cell to rupture if it is in a hypotonic solution or change shape without rupturing if it is in an isotonic solution. The LPS of Gram negative bacteria protects the peptidoglycan from being affected by lysozyme. When Gram negative bacteria is treated with ethylene diamine tetraacetic acid (EDTA), a chelator, this destabilizes the LPS allowing it to become permeable. The objective of this experiment was to demonstrate that lysozyme will cause bacteria cell walls to rupture, causing a decrease in population, depending on the osmolarity of its surroundings. Methods:
In this experiment three groups of samples were made. The first and second group contained Gram positive bacteria. The first group contained a population of Micrococcus that had been grown slowly and was still growing. The second group contained a population of Micrococcus that had been grown rapidly and was in the stationary phase. The third group contained a population of Gram negative bacteria. Each sample was placed in an HEPES buffer at a pH of 7.2 and concentration of 1.0 mM. This created a hypotonic solution.
The first and second group contained three samples each. The first sample was a control and contained only the buffer and the Micrococcus. The second sample contained the buffer, the Micrococcus, and the lysozyme. The third sample contained the buffer, the Micrococcus, the lysozyme, and KCl used to create an isotonic solution.