Phenylethyl Salt Agar

Introduction Life could not exist without microorganisms: plants depend on microbes to obtain soil and cows need microorganisms to digest cellulose. Microbes degrade waste and they live in our bodies to keep us healthy. Microorganisms are also used to make vaccines and antibiotics. However, some bacteria are known for causing diseases such as the common cold, AIDS, Herpes, and Chicken Pox. Knowing the identity of microbes is essential for knowing the causative agent of a disease in order to provide patient’s effective treatment. The purpose of this lab is to identify the unknown bacteria that was given. Applying all of the techniques that have been learned in the lab will help identify and distinguish the unknown bacterium. While identifying the bacteria, it is important to examine the morphology and characteristics of the bacteria. Identifying and studying bacteria can lead to possible cures for existing or future diseases. …show more content…
It is not a differential medium, but it is selective because Gram-negative organisms are inhibited by the phenylethly alcohol. Nutrient Agar was used to compare the growth quality of the organism to other mediums. Mannitol Salt Agar was another medium that was spot inoculated with the unknown. Mannitol Salt Agar is a differential and selective medium. Mannitol Salt Agar are composed of Phenol red pH indicator, mannitol, and 7.5% sodium chloride. The medium is differential because it differentiates and isolates Staphylococcus aureus from other Staphylococcus species. Staphylococcus aureus produces acid from mannitol fermentation by producing a yellow halo around the growth. Other Staphylococcus species will grow, but it will not ferment the mannitol. The medium is selective because it has a salt concentration, which allow Staphylococcus species to grow since they are used to living in high salt concentrations, for example, the human