Microbiology Lab Report
1. Title: The Process of Determining the Unknown Bacteria #9 Rachel Judecki July 5, 2011
2. Introduction: Each student was given unknown bacteria and was instructed to perform a variety of experimental tests that would help to identify their bacteria. During the process of identification, the unknown bacteria was added to many different testing medias using aseptic technique. They are as follows: lactose fermentation on eosin methylene blue (EMB), TSI (Triple Sugar Iron agar), Phenol red sucrose, the SIM test, H2S by SIM, IMViC (indole, motility, voges-proskauer, and citrate), Urease (urea broth), PDase (Phenylalanine Deaminase), Lysine Decarboxylase, and Ornithine Decarboxylase. Colonial morphology on EMB was used to prove the identity of the bacteria. The unknown bacteria was #9. After performing the tests it is determined that the unknown bacteria is Escherichia coli.
3. Methods: All tests were performed using the aseptic technique to assure the cultures were pure and not contamination was present. The inoculation loops and straight wire stab needles were placed over the flame of a Bunsen burner and heated until red hot (sterile) then cooled before placing them into the bacteria to prevent the killing of the bacteria. The open end of each tube of bacteria was flamed once it was open (before inoculation) and before it was closed (after inoculation). (Morello, 9th Edition. 2008) EMB (eosin methylene blue) agar was used to determine if the bacteria was a lactose fermenter or a non- lactose fermenter. EMB agar is a selective and differential media. The dyes eosin Y and methylene blue found in the medium inhibit the growth of gram-positive bacteria but not the growth of gram-negatives. Lactose fermenters metabolize the lactose in the media and produce acid byproducts, causing a color change in the colony which is dark purple, almost black. Strong acid productions by organisms result in a metallic green sheen. Weaker fermentation of
2. Introduction: Each student was given unknown bacteria and was instructed to perform a variety of experimental tests that would help to identify their bacteria. During the process of identification, the unknown bacteria was added to many different testing medias using aseptic technique. They are as follows: lactose fermentation on eosin methylene blue (EMB), TSI (Triple Sugar Iron agar), Phenol red sucrose, the SIM test, H2S by SIM, IMViC (indole, motility, voges-proskauer, and citrate), Urease (urea broth), PDase (Phenylalanine Deaminase), Lysine Decarboxylase, and Ornithine Decarboxylase. Colonial morphology on EMB was used to prove the identity of the bacteria. The unknown bacteria was #9. After performing the tests it is determined that the unknown bacteria is Escherichia coli.
3. Methods: All tests were performed using the aseptic technique to assure the cultures were pure and not contamination was present. The inoculation loops and straight wire stab needles were placed over the flame of a Bunsen burner and heated until red hot (sterile) then cooled before placing them into the bacteria to prevent the killing of the bacteria. The open end of each tube of bacteria was flamed once it was open (before inoculation) and before it was closed (after inoculation). (Morello, 9th Edition. 2008) EMB (eosin methylene blue) agar was used to determine if the bacteria was a lactose fermenter or a non- lactose fermenter. EMB agar is a selective and differential media. The dyes eosin Y and methylene blue found in the medium inhibit the growth of gram-positive bacteria but not the growth of gram-negatives. Lactose fermenters metabolize the lactose in the media and produce acid byproducts, causing a color change in the colony which is dark purple, almost black. Strong acid productions by organisms result in a metallic green sheen. Weaker fermentation of
Bibliography: Black, Jaquelyn G., Microbiology: Principles and Explorations, 7th Edition, John Wiley & Sons, Inc, Hoboken, NJ, 2008 Davis, Charles P.; Marks, Jay W., (2011) E. coli 0157:H7 (Escherichia coli 0157:H7 infection). Retrieved from: http://www.medicinenet.com/e_coli__0157h7/article.htm Morello, Josephine A., Mizer, Helen Eckel, Granato, Paul A., Laboratory Manual &Workbook in Microbiology: Applications to Patient Care, 9th Edition, McGraw-Hill Higher Education, New York, NY, 2008 Unknown author, Enterotoxigenic Escherichia coli (ETEC) page last updated: 11/25/2009. Retrieved on 7/2/2011 from: http://www.cdc.gov/nczved/divisions/dfbmd/diseases/enterotoxigenic_ecoli/