Microbiology Organisms

6 Pages 1375 Words

PURPOSE

To identify an unknown microorganism by performing a series of biochemical tests on a pure bacterial culture.


MATERIALS AND METHODS

1. CARBOHYDRATE FERMENTATION: In this experiment, I took two tubes of a liquid medium, one containing a phenol red sucrose broth and one containing a phenol lactose broth, and inoculated each one with the unknown organism#1. Both tubes also contained a Dunham tube which is used to form a bubble if gas is produced. The phenol red in the broth tubes is used to indicate alkaline and acidic conditions. Acidic conditions are determined by the medium turning from red to yellow while alkaline conditions are determined by the medium turning yellow and a bubble forming in the Dunham tube. Both the color change and gas production means that the organism can ferment sugar. Negative results are determined if the mediums remains red.


2. SULFITE INDOLE MOTILITY: The SIM test was performed by using a sterile needle and inoculating the tube in a straight line with the unknown organism. A positive test will show hydrogen sulfide being created and you would see a black precipitate formed.


3. 1% TRYPTONE BROTH: The tryptone broth test was just inoculating the unknown organism into the tryptone broth tube but also doing some extra steps after the incubation. After taking the tube out of the incubator, I had to see if any growth was formed in the tube and add 5 drops of Kovac’s reagent and then let it stand for 10 minutes. A positive test is determined if there is a red ring on the top layer of the broth confirming that indole is present. This means that the bacterium has the tryptophanase enzyme and can break tryptophan into pyruvic acid and indole. A negative result would mean no ring at the top and the tube remaining its same color, yellow.


4. UREA HYDROLYSIS: This test was also done by inoculating a tube of urea broth with my unknown organism. This medium is used to detect urea ...