Unknown Lab Report Microbiology Unknown A Sonia Kabra November 26, 2014 Introduction
There are numerous reasons for identifying unknown bacteria. Some of these organisms have distinct qualities that set them apart from one another, such as the exposure to certain environments. Through out the semester in the laboratory, we are able to encounter some of the few microorganisms that we as humans have come into contact with. With the knowledge gained from the sessions in the laboratory, we can now integrate what we have learned to the process of finding out the unknowns given. Materials and Methods
The professor gave out the unknown specimens. It contained one-‐gram positive and one-‐gram negative bacteria from the given list. I was assigned unknown A. The process of identification was achieved by utilizing procedures learnt during the semester. Procedures were followed as stated in the lab manual (1). Since the sample contained two unidentified bacteria, the first step was to isolate each bacterium using streak plate technique. Tryptic Soy Agar (TSA) plate, and differential media such as mannitol salt and Eosin methylene blue (EMB) were used for isolation streak technique. This step is imperative because the bacteria need to be separated and isolated before they can be identified. Moreover, gram staining was used to understand the basic morphology of these bacteria. As these plates were incubated and grown, the presence of two separate bacteria colonies was visible. The colonies from the mannitol salt were used to incubate a TSB broth to grow the gram-‐positive culture. The purity of this broth was tested using gram-‐staining technique. A circular colony from the TSA plate was used to
incubate a TSB broth for gram-‐negative growth. Similarly, examining the morphology of the bacteria-‐using gram staining technique tested the purity of the both. After the isolation of gram-‐positive and gram-‐negative bacteria from unknown A, specific biochemical tests were performed. The results of the biochemical tests along with deductive reasoning and elimination led to the identification the unknown bacteria. The following tests were performed on the gram-‐positive bacteria: 1. Mannitol salt streaking 2. Gram stating of the pure isolate 3. Oxidase test 4. Catalase test 5. Coagulase test The following tests were performed on the gram-‐negative bacteria: 1. Gram staining of the pore isolate 2. Blood agar plate streaking 3. SIM (Sulfide, Motility, Indole) test 4. Catalase test Results
Table 1. Biochemical Tests for the Gram-‐Positive Unknown TESTS PURPOSE REAGENTS/MEDIA OBSERVATION RESULTS Gram stain To determine the gram reaction and morphology Crystal violet, Iodine, Alcohol, Safranin
Purple cocci, connected Gram positive purple cocci
Mannitol salt Selective growth media for Staphylococci and Micrococcaceae
Mannitol salt plate and gram...