Lab Report

The next step of the project included preparing a Gram stain to discover the cell shape, arrangement, and if the bacteria is gram positive or

After several biochemical tests, Unknown Bacteria #30 was identified as Staphylococcus aureus. After growing the bacteria on Nutrient Agar to ensure a pure sample, it was Gram stained to determine morphology and arrangement. It was observed to be a Gram positive staphylococci. Then, the bacteria was inoculated onto a Mannitol Salt Agar plate. After incubation, it was observed to have bacterial growth and the agar was yellow in color. According to the lab manual (2), MSA contains 7.5% NaCl and phenol red, a pH indicator. Due to the salt content, MSA is selective for salt-tolerant bacteria and the phenol red allows MSA to differentiate for mannitol fermentation. Mannitol fermentation is indicated by a yellow color change, which is the result of acidic byproducts changing the pH of the agar. The results showed that the bacteria was both salt-tolerant and able to ferment mannitol.

In this investigation, the objective was to preform various test which were used to help identify an unknown bacterium. The tests done were a combination of selective and deferential media, plus a number of metabolism tests. The result of each test revealed a particular characteristic of the unknown bacterium, and using the combined results observed of these test the unknown bacterium was identified.

The color change was observed within 20 seconds. 12. Catalase Materials: Hydrogen peroxide, microscope slide, unknown 413, wooden stick Procedure: Aseptic technique was carried out to prepare working area. The wooden stick was to pick up some bacteria from the test tube. The bacterium was placed on the slide and a drop of hydrogen peroxide was placed onto it.

The MacConkey Agar is a selective and differential medium that is used to determine whether or not the bacteria can ferment lactose. The bile salts and crystal inhibits growth for gram-positive bacteria and cause color change. In this case there was no color change, but there was growth. This indicates a gram-negative bacterium. Upon further inspection, the pigment of the growth on the agar plate was beige with a circular colony form. The bacteria appeared raised, smooth and translucent. A sample of the

Escherichia coli is a Gram-negative rod that was tested on ten different biochemical testing procedures. The Escherichia coli culture on the MacConkey agar had growth and experienced fermenting of lactose (color change to yellow). This is an expected result because this agar only grows Gram-negative bacteria so it is a selective media. The bile salts and crystal violet are the agents that make the agar select against Gram- positive species. The pink tint is probably from the precipitation of bile salts. The Bacillus subtillis is a Gram-positive bacterium so it was not supposed to show growth or fermentation, but it showed growth without a color change (no lactose fermentation). This was due to the over streaking of maybe Escherichia coli or Enterococcus durans, which are Gram-negative species. Staphylococcus epidermis had a growth along with a yellow to orange color change. Media too was clear.

This experiment involves many qualitative tests to determine a mixed double unknown bacteria that contains two bacteria species; one gram-positive and one gram-negative. A dichotomous key was used in order to determine what tests needed to be conducted to define the particular bacteria. It is highly important for the tests to be followed as specified in the manual; otherwise, the bacteria could be falsely identified. Controls must be included in the testing to make sure there is something to compare the unknown results to. The tests conducted in this experiment included, gram stain, SIM, citrate, nitrate, oxidase, DNase, catalase, hemolysis, and novobiocin sensitivity. Through these tests one can conclude that the bacteria species present in the mixed unknown are Shigella

Abstract The purpose, or objective, of this lab was to identify an unknown bacteria by conducting different tests. Some of these include: oxidase test, fermentation tests, and catalase test. DNA fingerprinting was also conducted on the unknown sample, in order to provide another accurate means of identifying our DNA sample. The main objective for the identification lab was to be able to use known methods to identify our bacteria, including being able to follow a flowchart to aid in the process.

The Gram negative stain and rod shape eliminated six of the possibilities. The SIM (Sulfur Motility and Indole) testing proved that the organism was motile, was a gas producer, did not produce indole, and Triple Sugar Iron-Agar Slant produced a black butt and red slant indicating glucose fermentation and confirmed sulfur gas production, leaving only Proteus vulgaris as another possible outcome. Casein, gelatin, and urease testing were needed to conclude my results, as only P. vulgaris would be found to possess the enzymes casease, gelatinase, and urease, which, none of those were found in my unknown organism. Both of the two organisms were negative to hydrolyze starch, and neither can metabolize oxygen.

I inoculated an Eosin-Methylene Blue (EMB) agar plate and a MacConkey agar plate using Alderson’s streak plate technique (Alderson, 2015, pp. 64-65). Next, using Alderson’s procedure for aseptic techniques for inoculation (Alderson, 2015, p. 53) along with the procedures for each individual test I conducted the biochemical tests on 1 lactose Durham broth (Alderson, 2015, p. 267), 1 glucose Durham broth (Alderson, 2015, p. 267), 1 TSIA slant (Alderson, 2015, p. 267), 1 SIM agar (Alderson, 2015, p. 268), 2 MRVP broths (Alderson, 2015, p. 268) and 1 citrate agar (Alderson, 2015, p. 268). I also tested my microbe’s ability to produce oxidase (Alderson, 2015, p. 267). Finally, I tested for the presence of catalase (Aryal, 2015, para.

This is a multipurpose media that allows to study three different characteristics of bacteria: sulfur reduction, indole production, and motility (SIM). These traits are very useful to identify gram-negative

The Bacteria A cells that were pink/red in color after the addition of the Safranin stain were the Gram-negative cells. Gram-negative cells have higher lipid content in their walls; therefore they lose the primary stain color after the decolorization step. After the Gram-negative cells were counterstained with Safranin, they turned pink or red, whereas Gram-positive cells remained purple. After the isolation of the Gram-negative bacteria, a variety of tests were performed to identify the unknown bacterium as Shigella flexneri. Of the three Phenol Red broth tests, the PR Glucose broth test was the only one whose results were positive as indicated by the change in broth color from red to yellow and by the presence of bubbles in the tube. These results indicate that the bacterium was able to ferment glucose with acid and gas end products. The bacterium was unable to ferment sucrose or lactose as the broth in both tubes remained red and no bubbles were present. Just from the Phenol Red broth results, the unknown bacterium could either be Salmonella typhimurium or Shigella flexneri. The results from the Methyl Red and Voges-Proskauer tests show that the bacterium was able to perform mixed acid fermentation but could not ferment glucose where its acid products would quickly convert into 2,3-butanediol and

The Catalase test is performed on organisms to see if it can produce the enzyme catalase. According to Michael J. Leboffe and Burton E. Pierce (2012), bacteria that produce catalase can easily be detected using store-grade hydrogen peroxide. When hydrogen peroxide is added to a catalase-positive culture, oxygen gas bubbles form immediately. If there are no bubbles produced then the organism is catalase-negative. If you are unable to see the bubbles with your eyes, you may have

For the ability to ferment glucose, M. luteus does not have the ability to ferment glucose Two tests were performed. The first glucose media test had a mismatch observed versus expected result. While the second test, Kilgler’s Iron Agar had a match with the observed and expected results. The reason of this contradiction for the two tests seems to be one of the following possibilities: the first reason, an environmental effect that led to the contamination of the test either before or during incubation, which caused a positive test for glucose fermentation. The second reason could be a technical problem during the incubation period such as inappropriate conditions while incubation like the change in temperature, or the change in the proper incubation circumstances. Moreover, the microbe could have produced acid while growing aerobically which caused a false positive result. All reasons have a high possibility of causing a false positive result. This mismatch was derived after performing the Kilgler’s Iron Agar on M. luteus organism twice, and having a negative glucose fermentation for both trials.

After inoculating two cultures from a liquid test tube that was given by the instructor, several different test were performed in order to identify the each culture's characteristics. By comparing all the results to the unknown key chart, Unknown #1 concluded to be Staphylococcus epidermidis. It ended up negative results for gelatinase test, casein hydrolysis, oxidase test and motility test; while positive results for catalase test, nitrate reduction and MSA plate. The phenol red broths test showed that S. epidermidis had the ability to ferment when glucose, lactose or sucrose is present; however it did not have the ability to perform fermentation with the presence of mannitol. Unknown #2 concluded to be Shigella flexneri since it tested negative