Double Unkown Final Project

Topics: Bacteria, Microbiology, Bacteriology Pages: 12 (1252 words) Published: February 12, 2015
1. Title:
Double unknown identification of a mixed culture of Gram-negative and Gram-positive bacteria 2. Author:
Nick Fiore, University of Kansas, Biology 402, Fall 2014 3:00pm room 6040 3. Abstract:
The purpose of this experiment was to isolate two unknown bacteria and perform a series of selective and differential tests to correctly identify each. After the bacteria was isolated a series of differential and selective tests following the dichotomous key attached were used to identify each bacteria. The Gram-positive bacteria were identified as Staphylococcus aureus with a positive confirmatory test, mannitol salt agar, showing consistent results as well for S. aureus. The Gram-negative bacteria were Pseudomonas aeruginosa with a positive confirmatory test, the citrate test, showing results consistent with P. aeruginosa. 4. Introduction:

The purpose of this experiment was to isolate two unknown bacteria and perform a series of selective and differential test to correctly identify each. Many different tests were utilized in this experiment all of which were done either to isolate or differentiate the bacteria from other bacteria. Some tests were done on selective media to inhibit the growth of other bacteria and aid in identifying the bacteria after taken from single colonies. Some other tests were performed on differential media, which was done to distinguish the bacteria from others like it. All of these tests and their results were used in combination with one another to aid in correctly identifying the bacteria. Identifying a mixed culture of unknown bacteria has many practical uses in real life situations including; isolating pathogenic bacteria from a patient’s culture, identifying particular bacteria in the food industry for various reasons whether purposefully in products or in contaminated products, or many other uses throughout healthcare and industry. 5. Experimental Procedures:

The mixed bacterial culture was streaked for isolation onto a nutrient agar plate. After ample time for growth isolated colonies were Gram-stained and examined under microscope and subsequently streaked onto selective media for either the Gram-negative bacteria or the Gram-positive bacteria. Following the selective media growth each bacteria was tested according to the results of the previous tests performed on it. The tests performed are in the following graphs in the order performed with one graph corresponding to the Gram-negative species and one for the Gram-positive. Gram-negative sample and the tests utilized on it

Test utilized
Reference
Gram-Stain
Microbiology: Laboratory Theory & Application
Hektoen Enteric Agar
Microbiology: Laboratory Theory & Application
Eosin Methylene Blue
Microbiology: Laboratory Theory & Application
Sulfur Indole Motility (SIM)
Microbiology: Laboratory Theory & Application
Citrate Test
Microbiology: Laboratory Theory & Application

Gram-positive sample and the tests utilized on it
Test utilized
Reference
Gram-stain
Microbiology: Laboratory Theory & Application
Catalase test
Microbiology: Laboratory Theory & Application
Glucose Fermentation test
Microbiology: Laboratory Theory & Application
Gelatinase test
Microbiology: Laboratory Theory & Application
Mannitol Salt Agar
Microbiology: Laboratory Theory & Application

6. Results:
The following tables are each corresponding to either the Gram-positive sample or Gram-negative sample and include the tests utilized along with their results all in the order each test was performed. In section 10, Figures, there are some pictures corresponding to the stains performed. In Figure 1, the Gram-positive stain, you can clearly see the purple color and cocci morphology in grapelike clusters. Figure 2 is the Gram-negative stain with the safranin color and shows bacilli cellular morphology. Gram-positive sample

Test Utilized
Result
Controls
Gram Stain
Gram-positive cocci
Positive-S. epidermidis
Negative- E. coli...


References: Leboffe, Michael J., and Burton E. Pierce. Microbiology: Laboratory Theory &
Application. 3rd ed. Englewood, Colorado: Morton, 2010. Print.
10. Figures:
Figure 1.
Figure 2.
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