Chelsea Herron

Micro Lab Unknowns Dr. Laura Ong

November 19, 2013

Unknown #4

It is advantageous for the student to gram stain the unknown microbe to narrow the field of possibilities as seen in figure 1. Once the gram staining process is complete the student

may view his/her microbes under a microscope. Pink colored rods indicate microbes with gram (-) membranes as seen in figure 2. If the microbes are found to be gram (-) the student may

begin by conducting a MacConkey test as seen in figure 3. A positive test leads to the possibility of Escherichia coli or Klebsiella pneumonia. Using an inoculated loop the microbes will be transported to the MacConkey plate and incubated for twenty-four hours. A positive test appears opaque as opposed to transparent. The student may then conduct a Urease

Production test. A positive result is seen when urea comes into contact with urease to produce ammonia which makes the medium turn a bright pink color as seen in figure 4. The results are viewed twenty-four hours after incubation where a positive test gives evidence for the presence of Proteus vulgaris and Klebsiella pneumonia. He/she may then perform a TSIA (Triple

Sugar Iron Agar) test as seen in figure 5. An inoculated loop will be used to transfer microbes to the TSIA tube. The loop will be used to penetrate through the center of the agar avoiding the

sides of the tube. The TSIA will be incubated for twenty-four hours. In a positive test the medium will become a bright yellow color and the area near penetration will be black. This will

give rise to the presence of Proteus vulgaris and Salmonella typhimurium. Since this microbe tested positive for the Urease and TSIA tests it is most likely Proteus vulgaris.

Figure 1 Figure 2

Figure 3 Figure 4 Figure 5

Unknown #4: Proteus vulgaris

Chelsea Herron

Micro Lab Unknowns Dr. Laura Ong

November 19, 2013

Unknown #36

It is advantageous for the student to gram stain the unknown microbe to narrow the field of possibilities as seen in figure 1. Once the gram staining process is complete the student may view his/her microbes under a microscope. Violet colored cocci indicate microbes with gram (+) membranes as seen in figure 2. The student then may conduct a catalase test to determine whether the microbes are Staphylococcus or Streptococcus. He/she will add a few drops of hydrogen peroxide to the slide. Staphylococcus will have an immediate reaction with the hydrogen peroxide causing bubbles to form while Streptococcus will appear inactive. If the microbe tests positive for Staphylococcus the student may proceed by performing a coagulase

test as shown in figure 3. A positive test will show coagulation within thirty seconds as the

microbes seem to clump into groups which would determine if the microbe might be Staphylococcus aureus. In this case the coagulation test was negative. An MSA (Mannitol Salt Agar) test may also be conducted to determine if the microbe may be Staphylococcus epidermidis as seen in figure 4. An inoculated loop will be used to transport fresh microbes to a plate filled with Mannitol salt agar and then placed in an incubator for thirty hours. A positive test will turn the agar from a pink color to a bright yellow color. A hemolysis test can also be conducted to determine if the microbes can break down red blood cells. A complete lack of hemolysis leads to the conclusion that the microbes may be Micrococcus luteus as seen in figure 5. After incubating the plate for thirty hours a positive hemolysis test will show a clear zone around the microbe colonies.

Figure 1 Figure 2 Figure 3

Figure 4 Figure 5

Unknown #36: Micrococcus luteus