Unknown Lab Report

The first step toward identifying this unknown organism was to perform a Gram Stain to differentiate between gram positive and gram negative bacteria. This is an important step because it directs what the next tests will be. My Gram Stain on sample #12 showed that the bacteria was gram negative, however, after receiving the results of the OF glucose, H2S, Citrate, Urease and Motility tests, it was apparent that my Gram Stain was contaminated. I then performed a catalase test which came back negative, so I ordered a Bacitracin disc, Optochin disc and a CAMP test which had to be incubated overnight. After receipt of those test results,

Negative result is no color change with mineral oil on top of solution. This bacterium has +/- reaction on MAC plate. It could survive in an acidic environment, but it not able to ferment lactose. The bacteria grow on the plate, but did not change the color of the plate to bright pink. This bacterium has a +/- result on Bile Esculin Agar.

Thus we inoculated lactose broth, glucose broth and tryptophone broth with our organism. At our final lab meeting, we observed that the lactose broth was still phenol red in color, glucose tube had turned yellow with a bubble present in Durham tube, and the oily ring in our Indole test was colorless. Taking all the results into consideration and rechecking all of our steps against the guidelines and steps to ensure all required tests had been performed, we concluded that our organism belonged to Group IX genre, Proteus, Providencia, and Morganella. We then proceed to consult with our instructor.

The oxidation fermentation test was used to differentiate if the organism utilizes lactose, mannitol, glucose and citrate aerobically (oxidation) or anaerobically (fermentation). A methyl red test was performed to determine if the organism carried out mixed-acid fermentation when supplied glucose. A Voges-Proskauer test was performed to evaluate if the unknown was able to ferment glucose into butanediol. A citrate test was performed to determine if the unknown organism was able to break down citrate into ammonia. An oxidase test was then performed to determine if the unknown culture was oxidase positive or negate.

For this experiment, I utilized unknown number three which I later identified as Staphylococcus epidermis. I concluded that the unknown organism was Staphylococcus epidermis based on numerous tests performed in the laboratory which I will discuss in detail throughout this paper. One of the first tests performed was the Gram Stain. The Gram Stain

5) One final test was run on the sample and that was the EMB test. Results of this test showed little to no growth on the EMB plate while the color of the colony (although barely visible) remained the same color as the agar. This test is selective for gram negative bacteria but inhibits the growth of gram positives. It also is differential in that it can test whether a bacteria can ferment lactose. Due to the fact that there was virtually no growth (a very faint haze) and no color change of the agar, the sample can be said to be gram

To do this, one must use a series of biochemical tests. These tests will investigate the bacterium’s ability to use available enzymes and degradation of specific carbohydrates, lipids, proteins and amino acids. The use of these organic compounds will produce byproducts that can be observed to determine the metabolism of the unknown bacterium. One of the first biochemical tests that I prepared was the S.I.M. test, which is a combination of three tests in one test tube. The “S” represents sulfide for the sulfur reduction test. This individual experiment detects hydrogen sulfide production. If the unknown bacterium has either cysteine desulfurase or thiosulfate reductase it will be able to reduce sulfur to a hydrogen sulfide gas. Once H2S is produced, it combines with the ferrous ammonium sulfate, forming a black ferrous sulfide precipitate that can be seen along the original stab line; the presence of black along the stab line would indicate a positive result. This test can also be used to detect the presence or absence of motility. This observation is what makes up the “M” in the S.I.M. test for motility. The only thing that needs to be done for this test is observation. If there is growth away from the stab line, then that indicated that the unknown bacterium is motile. If there is no growth away from the stab line, then that indicates no motility and a negative result. Unk#19 presented with black precipitate as well as growth away from the stab line. After completing the motility and sulfide tests, I could then perform the indole test. The purpose of this test is to find if the unknown bacterium contains the enzyme tryptophanase can break down the amino acid, tryptophan, into its three metabolic ingredients: indole, pyruvic acid, and ammonia. If the bacterium contains tryptophanase, they will then use ammonia and pyruvic acid for nutritional needs,

pneumoniae) leaving me with Sa, Se, Ef, P.pyo, and Ml. Following my dichotomous key, the next test I decided to perform was a catalase test in order to determine if the enzyme catalase is produced by the bacteria. The sample of the bacteria I took did bubble, this indicates that the bacteria does produce the catalase enzyme as well as requiring oxygen to respire. Based on the results of the catalase test there were three possible microbes I could have Ml, Sa, and Se. For my next test I decided to use an MSA plate to determine if my unknown microbe could or could not grow in the presence of the mannitol salt, along with testing to see if it would or would not be able to ferment the mannitol salt. After allowing the bacteria to grow, I noted that the plate remained the same pinkish color it originally was however, I did several white colonies growing on the plate. The pink color that remained shows that the organism is unable to ferment the mannitol salt thus the acidic byproduct that turns the medium yellow will not be produced. Therefore the organism cannot be Sa since that

A total of 13 tests were performed on the unknown bacteria culture #1. Two tests were inconclusive and could not be used. The first test was simply the phenylethyl alcohol agar (PAA) to check for contamination because of its selectivity towards gram-positive bacteria. The alcohol in the agar penetrates the thin peptidoglycan wall of gram-negative bacteria, which results in a slowed and stopped growth. The mannitol salts agar (MSA) is a differential test due to the mannitol sugar. It also has high amounts of salt (7.5% NaCl). If the organism can ferment the sugar, and produce acid as a result, the phenol red pH indicator dye will turn yellow due to the acidic environment. If no change occurred, then it is a negative result meaning that the bacteria

After the multitude of tests performed, it was determined that the bacterial unknown was Staphylococcus aureus. The gram stain slide was positive. The morphology and arrangement was grape like cocci clusters. On the glucose fermentation test the bacterial unknown tested positive for acid and negative for gas. The oxidase test was negative. The bacterial unknown tested positive for catalase. In the litmus milk medium a K or alkaline reaction was observed. It tested negative for urea hydrolysis. The bacterial unknown tested positive for nitrite. On the Kigler 's iron agar media it tested negative for gas, positive for glucose, positive for lactose, and negative for hydrogen sulfide. On the SIM medium media it tested negative for indole, negative for hydrogen sulfide, and negative for motility. The bacterial unknown tested negative for methyl red. It tested negative for Voges-Proskauer. It tested negative for citrate. It tested

When studying unknown bacterial organisms, microbiologists use a wide variety of techniques to observe the organism’s traits and classify it. Many genotypic and phenotypic methods exist that aid in the identification of known bacteria, the characterization of unknown bacteria, as well as the comparison between new findings and

The purpose of this experiment was to identify an unknown microbe with the knowledge we have obtained from previous experiments. We used our knowledge of staining properties, cell morphology, cell arrangement, and biochemical tests to identify the microbe. Our professor provided us with a flowchart to guide us through the elimination process of this experiment.

Problem: An unknown bacteria in test tube #13 needs to be identified out of the list of bacteria provided as possible. Hypothesis: If different tests were carried out to identify the bacteria’s characteristics, then the bacteria could be identified, because a dichotomous key can be used to eliminate all other bacteria in the list Procedure: 1. Obtain an inoculating loop, Bunsen burner, test tube #13 and a test tube rack. 2.

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

Over a three week time span I was able to successfully identify an unknown microorganism by combining the results of several tests. The first test was the Gram stain test which showed the microorganism was Gram positive and rod shaped. Using an Unknown Identification Flowchart, I proceeded to inoculate a Starch plate. In week 2, I analyzed the Starch plate and was able to determine that the results for Starch Hydrolysis were negative due to the dark color. Next, I inoculated Simmons Citrate Agar slants. By week 3 I was able to analyze the Citrate Agar, which tested negative