Motility Agar Lab

For the motility portion of the motility and chemotaxis lab, I hypothesized that there would be movement seen for Proteus mirabilis, however there would be no movement for Staphylococcus aureus. I expect these results to occur because the motility agar contains tetrazolium salt, which in its oxidized state the salt is colorless, however when living bacteria is present within the media they reduce the salt content of the medium causing a purple color to display. Therefore when a living organism comes in contact with the salt, the medium will turn purple, this will allow the tetrazolium salt to act as a tracer for movement of the bacteria. This indicates that proteus mirabilis is a living organism and will move from the point of inoculation and spread throughout the medium, displaying a purple color; while the non- living bacteria, Staphylococcus aureus will only grow at its point of inoculation, revealing the purple color on in the site of inoculation.