Microbiology 150 Lab 3-Selective vs. Differential Media

The following tests according to the lab manual were performed: gram stain, fermentation tubes, methyl red, vogues proskauer, sulfur, indole, motility and growing it up on MacConkey agar. The gram stain was performed incorrectly the first time. This is because the decolorizer was not on the bacterium slide for long enough, giving a false outcome.

This experiment was centered on metabolic and biochemical testing procedures. The rationale of performing these tests was to distinguish six different microbes from one another and to compare how their metabolic and biochemical processes differ from species to species to determine the unknown sample.

11. An important tool available in the Virtual Unknown program is the Identification Matrix. From the portion of the identification matrix shown in the Identifying Bacteria tutorial, identify at least one bacterium that has a positive result to the arabinose fermentation test. (1 pt)

I began by running the starch test, which tests for the presence of starch hydrolyzing enzymes. After doing a one-line inoculation of the organism, the plate had to be incubated. Once I received an appropriate amount of growth I added the reagent iodine. The iodine turned the plate purple, formed no clear zone, and lifted the organism off of the plate, which revealed that the starch was not degraded and the enzyme was not present. The organism being lifted off the plate is unique to the bacteria Corynebacterium xerosis indicating that it was my gram positive rod. For reassurance, I ran the Phenol Red Glucose test, which tests if the organism contains various enzymes that determine if the bacteria can ferment glucose. After incubation, the broth turned orange, but this did not provide a clear positive or negative result so I ran the Nitrate Broth Reduction test. The Nitrate Broth Reduction test detects if the organism utilizes nitrate. After incubation for forty-eight hours I added Nitrate A and Nitrate B indicators. However, there was no color change indicating that the test was inconclusive. Since the test was inconclusive, I proceeded to the following step, which included adding a small amount of zinc to the broth, and this turned the broth a red color. The red color indicated that

This test is used to detect if the bacteria contains any deoxyribonuclease activity. Because no color change was observed from blue to clear my unknown bacteria displayed a negative result.

Purpose: The purpose of this lab is to help you become a little familiar with some of the tests that can be typically performed in a clinical or research lab facility. These tests may help in determining a particular pathogen’s growth needs.

The purpose of this lab was to identify unknown bacteria cultures using various differential tests, and my unknown bacteria is #17. The identification of these unknown cultures was accomplished by separating and differentiating possible bacteria based on specific biochemical characteristics. Whether the tests performed identified specific enzymatic reactions or metabolic pathways, each was used in a way to help recognize those specifics and identify the unknown cultures. The differential tests used to identify the unknown cultures were Gram stain, Catalase, Mannitol Salt Agar (MSA), Blood Agar, Novobiocin, Coagulase, and DNAse (Alachi, 2007).

There are many reasons for knowing the identity of microorganisms. The reasons range from 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 unknown bacteria. The identification process can be completed with a series of deferential stains and biochemical tests. Creating a dichotomous key helps to limit the amount of biochemical tests done on an unknown organism and by observation

The goal of this experiment is to determine the blood types of the samples given and to learn what interactions occurred to each blood type. Determining an individual’s blood type and how it reacts with Anti A, Anti-B, and Anti Rh serums played a crucial part in this experiment. The researcher concluded that agglutination (clumping) occurred in some of the blood samples. For example, Mr. Smith’s blood reacted with Anti-A and Anti-Rh serums (antibodies) allowing the researcher to determine the blood type is A. Mr. Jones’s blood reacted with Anti-B serum but it did not react to Anti-A or Anti Rh allowing the researcher to believe that the blood type is B. Mr. Green’s blood reacted with all serums and caused a reaction to occur resulting the blood type to be AB positive. Mr. Green’s blood also had a positive marker for Rh factor. However, Ms. Brown’s blood had no reaction at all and the researcher determined if no reaction occurred then the sample had no antigens but proved to have some antibodies, resulting in blood type to be O. The purpose of this experiment is to determine whose blood has type A, B, AB, or O.

For the temperature test each bacteria was placed on a nutrient agar and incubated for either 10, 20, 30, 40, or 50 degrees Celsius for 48 hours. During the pH test, each organism was placed on four agars varying in pH level from pH 2, 4, 6 and 8 and incubated near 37 degrees Celsius for 48 hours. For the osmotic pressure test, each organism was placed on four agars one each containing 2%, 5%, 8%, and 11% NaCl concentration levels. These were incubated near 37 degrees Celsius for 48 hours. The results of the tests are recorded in Tables 1, 2, and 3. All tests were performed according to the instructions provided in Leboffe & Pierce(1). The biochemical tests used on both unknowns and the ubiquity are:

To identify red blood cells, basophils, eosinophils, monocytes, lymphocytes, neutrophils, sickle cell anemia and leukemia.

Hemolysis is when the rbc’s (red blood cells) membrane breaks causing the hemoglobin and contents of the cell to leak into the surrounding fluid. Autoimmune hemolysis is when your immune cells destroy your rbc (red blood cells) by mistake. The red blood cells are need to transport oxygen and nutrients through the body.

This lab and its procedures are all about finding out the unknown identification of a given bacteria. The lab consists of specific techniques, tests, chemicals, and vocabulary that are necessary for the finding of the bacterial identity. A bacterium is randomly assigned and it is a group effort to find the bacteria name through many of its specialties and characteristics. An example of classifying it would be to determine whether the bacteria is catalase negative or positive, or if the species is gram negative or positive. This lab is of huge significance because of its medical microbiology connections. Scientists Gurtler and Stanisich explained the connections more eloquently. They stated, in their medical article, that, “Medical microbiology

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

Another purpose of this experiment is to stress the importance of knowing the identity of a microorganism. Knowing the species of microorganism present in a sample provides a