Gram Negatives

An unknown bacterium was handed out by Dr. Honer. The appropriate tests were prepared and applied. The first procedure that was done was the gram stain. Under a microscope, if the gram stain is purple, the bacterium is gram positive, if the stain is red, it is gram negative. The next test was the fermentation tests for glucose, sucrose and

The colonies were smooth, translucent, and had a white brownish color. The Gram stain resulted in Gram positive cocci. After the Gram stain was completed, the bacteria were streaked on a Mannitol-Salt Agar plate and a Catalase test was performed. After these test were completed a Phenol Red Dextrose Fermentation tube was inoculated, and a SIM Tube inoculated.

The first result of importance was the result of the Gram stain. The observations of the unknown bacteria from the slant culture after Gram staining showed that the unknown bacteria were Gram negative bacilli (Image 1). After determining the unknown bacteria was Gram negative, an oxidase test was conducted on a sample from the slant culture. The cotton swap with the sample of bacteria did not change color when the oxidase reagent was applied, thus providing a negative result. With a negative oxidase test, further tests were conducted to determine various characteristics of the unknown bacteria. A MR-VP broth was inoculated with a sample from a slant culture of unknown bacteria. After incubation, the methyl red reagent was added to the broth, and the broth turned red, providing a positive result (Image 2). An EMB agar streak plate was inoculated with a sample from a slant culture of the unknown bacteria, and after incubation, growth was found on the plate, providing a positive result (Image 3). A Citrate agar slant was inoculated, and after incubation, growth was found on the media, providing a positive result (Image 4). A Urea agar slant was inoculated, and after incubation, the agar had changed from a peach color to a bright pink color, providing a positive result (Image 5). Using the flowchart (Figure 1) developed from the Table of Expected Results, the lab partners started at the oxidase test. Given the negative result of the oxidase test, the flowchart is

The unknown bacteria plate chosen was plate #2. It was identified to be Micrococcus luteus. It is a gram positive, Coccus bacteria that is commonly found in dust, water, soil, and the air. M. luteus also thrives in the human mouth and upper respiratory tract. Sir Alexander Fleming discovered it in 1928 before he identified penicillin. It is part of the normal flora on human skin as well as other mammals. Since it is part of normal flora it is normally not pathogenic, but can become opportunistic in an immune-deficient person. It has been known to cause septic shock, UTI’s, and even pneumonia. Micrococcus luteus is both urease and catalase positive. It does not utilize tryptophan for indole production. It is a facultative anaerobe. Mobility is not present for this bacterium. Starch is also not hydrolyzed and oxidase is not present.

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

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.

Next I performed a KOH test to further confirm that my organism was a Gram-negative species. For the KOH test, I added 3 drops of 10% potassium hydroxide (KOH) to a small drop of distilled water onto a clean microscope slide, transferred a visible clump of organism to the KOH solution using my inoculating loop. I than mixed the cells into the solution using small, circular motions for 60 seconds and then lifted up the loop to look for what appears to be a “stringing” affect which means it’s confirmed that it is gram- negative species. Next, I created a streak plate using nutrient agar so that I could see pure culture of my organism. I aseptically obtained a loop full of my organism and gently inoculated one quarter of the nutrient agar plate by running the loop back and forth across the surface. I then flame sterilized the inoculating loop, allowing it to cool for 10 seconds, and then streaked the organism from quadrant I into quadrant II using a zigzag motion technique. I repeated those steps streaking from quadrant II to quadrant III and then streaking from quadrant III to quadrant IV. Once completed, I put the streak plate in the incubator at 37° for 24-48 hours. 48 hours later, I check my streak plate and it had a lot of growth on it. I was able to determine that the organism was definitely an off white color, opaque. The IV quadrant was the quadrant that best

I do believe that my bacterial lawns contained only one species of bacteria on each plate, they are consistent in color and appearance from the bacteria colonies from Experiment 1. There is only one difference and it involves plate 1, the toilet handle. I was unsure if it was because of the bacteria or in reaction to the antibiotics but around the Kanamycin ZOI there is a brighter yellow ring around it. I thought it was strange that only around there was such a reaction but as I said I was not sure if it was a reaction to the Kanamycin.

This experiment was conducted to find the genus and species of an unknown bacteria prescribed by the lab teacher, which was unknown bacteria GA3 in my case. Identification of unknown bacteria techniques are used on an every day basis to figure out what type of bacteria it is and to find the best method of how to treat a patient with this bacteria (1). All five “I’s” of Microbiology were used in the testing for the unknown culture. Inoculation was used several times to put the unknown culture into agar plates or into biochemical test tubes. After Inoculation of these tubes or plates, they always were placed into the incubator for further growth and development. Isolation was used to make sure we got the correct bacteria we were testing for. After each further isolation, we gram stained the culture and inspected the culture under a microscope to further help in the identification process of the unknown bacteria. Multiple tests were done on the unknown culture to make sure we were confident in what kind of bacteria the unknown was.

The main idea of this experiment was to correctly identify the unknown bacteria, #3. Identification of unknown bacteria yields multiple benefits in many different areas in the research of microorganisms. In this experiment I performed many different test dealing with things such as the presence of enzymes, fermentation abilities and different chemical reactions. Observations made from the tests were then compared to a gram negative unknown chart in order to identify the bacteria. Based off of my results and the chart, I concluded the bacteria #3 was the bacteria Escherichia coli. E. coli is most commonly found in the intestines of warm blooded organisms. Most E. coli strands are non pathogenic however, there are strands

This lab experiment was done for the purpose of learning how to determine a gram negative bacterium based on multiple tests learned throughout the semester. My gram negative unknown bacterium given to me was Salmonella typhimurium based off of the following tests; Triple Sugar Iron Agar (TSIA), Sulfate Indole Motility (SIM), Methyl Red (MR), Voges-Proskaur (VP), Citrate, Urea Hydrolysis, and Gelatin Hydrolysis. Each test performed gives results such as motility, acid production, fermentation, carbon requirements, or detection of certain coenzymes. With a process of elimination, I determined which bacteria it was not and which bacterium I had, S. typhimurium. The expectation was to master the techniques for each test and utilize the results to determine the unknown bacterium I was given within a two-week period.

Two smears of the unknown bacterium #5 were inoculated while the second smear was used for a back up. The unknown bacterium dried for at least forty minutes. After the smears dried, the slides were heat fixed two times to ensure the stability of the organism. The slide was placed on top of the staining rack then over the small sink.

In the world of microbiology it is vitally important to be able to discern the identities of microorganisms. Not only is it important in a lab setting but as well as in healthcare in general. Properly identify what strain of bacteria a person has will aid in the proper medicine and dose given. Throughout the semester we have learned about different types of bacteria and certain test that can clearly identify them. The purpose of this lab report is to identify a Gram-positive or Gram-negative bacterium. Using all the knowledge of procedures and lab techniques identify the unknown and discuss all the tests you performed.

The bases of this experiment was to discover the identify of the unknown from three possible specimens: Klebsiella pneumonia, Escherichia coli, and Enterobacter aerogenes. Utilizaing the T streak technique, the bacteria was isolated into pure colonies for further study. The Gram Stain method was used to identity the morhphology of the bacteria such as the shape and whether the bacteria was Gram positive or Gram negative. Biochemical test were also used to help identify the unknown bacteria. The biochemical test used was the Triple Sugar Iron Agar, Sulfur Indole Motility test, Methyl Red test, Voges-Proskauer test, Citrate test, Urease test, and the Gelatin test. After observing the morphology of the bacteria using the Gram Stain method and utilizing all the possible biochemical test, the bacteria was identified to be Enterobacter aerogenes.

The bacteria that was contained within Unknown tube #12 is believed to be Pseudomonas aeruginosa, Figure 1. The bacteria tested to be Gram Stain negative, producing a pink, red color retained from the staining process. When the species of bacteria was plated on nutrient media, the cells produced an irregular and spreading configuration as shown in Figure 2. This same plating test provided the margins and elevation, lobate and hilly, respectively. The specimen was stabbed in a Fluid Thioglycollate Medium (FTM) tube using an inoculated loop of the bacteria. The results of this experimentation indicate the type of oxygen requirement of the bacteria. The test found the bacteria to be aerobic as colonies of the bacteria began to form along the top of the FTM tube (Manual 2017).