Microbiology Unknown

Topics: Bacteria, Enzyme, Glucose, Gram staining, Microbiology / Pages: 5 (1005 words) / Published: Jun 19th, 2006
Ron Williams


Bio 205

Prof. Curlee

Fall 2005


There are many reasons for knowing the identity of microorganisms. The reasons range from the knowing the causative agent of a disease in a patient, so as to know how it can be treated, to knowing the correct microorganism to be used for making certain foods or antibiotics. This study was done by applying all of the methods that have been learned so far in the microbiology laboratory class for the identification of an unknown bacterium.

By slowly narrowing down the bacteria by each test, I will be able to conclude the unknown bacteria by its special characteristics.


An unknown labeled as #54 was given out by the lab instructor. The methods that have been learned thus far for identifying bacteria have been applied to this unknown. Procedures were followed as stated in the course laboratory manual, unless otherwise noted. The first procedure that needed to be done was to streak the unknown out on a Trypticase Soy Agar plate, using the T streak method. This needed to be done in order to test the purity of the unknown. After the plates were incubated and grown, the morphology was observed and recorded and a Gram stain was performed. After determining the Gram reaction, specific biochemical tests were performed. The biochemical tests were chosen from the unknown identification tables that were in the lab manual. Since the unknown #54 was determined to be a Gram positive rod, a thyoglycollate test was performed to determine aerobic activity. Table 1 lists the test, purpose, reagents and results. All of the following tests were performed on this unknown:

1 Colony Appearance
2 Motility
3 Gram Stain
4 Thyoglycollate – aerobic vs. anaerobic
5 Innoculate T soy slant
6 Optimum growth temperature 37o vs. 42o
7 Nitrate test
8 Methyl Red
9 Carbohydrate fermentation
10 Catalase Test
11 Oxidase test

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