Lab Report On Microbial Unknowns Essay

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.

The purpose of this lab was to identify an unknown bacteria culture using differential tests. The identification of the unknown culture was accomplished by identifying the bacteria based on its specific metabolic characteristics and morphology. It is suggested that culture 11 is a sample of Enterobacter aerogenes.

The purpose of this lab was to identify two unknown bacteria from a mixed culture. The reason for identification of unknown bacteria was to help students recognize different bacteria through different biochemical tests and characteristics. This is important in the medical field because identification of unknown bacteria can help treat a patient by knowing the contributing source of a disease. Also knowledge of different bacteria helped others make antibiotics used today. This lab was completed by using the methods learned thus far in identification of bacteria.

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

The purpose of this lab was to identify two unknown bacteria cultures using various differential tests. The identification of these unknown cultures was accomplished by separating and differentiating possible

|EMB Agar | |Distinguishes bacteria that ferment |Dark blue colonies with|E. coli and P. |

Citrobacter Freundii is a species of bacteria that can be potentially harmful to humans. It is known to cause meningitis by protruding into the brain and replicating itself (1). The Citrobacter species has also been found as a cause of some urinary tract infections, diarrhea, and even gastrointestinal diseases and symptoms (3). C. Freundii can be located in a wide variety of soils and water (3). Lastly, it is also the cause of many nosocomial infections due to its presence in water (1).

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.

Lastly, safranin was added to flood the slide and was left on for 1 minute and rinsed with distilled water. After adding all 4 reagents, the slide was blotted dry with a paper towel to remove any excess reagents or water. The slide was then placed on a microscope stage to look for the color of the bacteria. When ready for the highest power on the microscope, immersion oil was added to the slide and looked at under 100x power. A glucose test and citrate test were found to be the best two tests to help narrow down the bacteria.

In class, we were given the task of identifying an unknown bacterium broth culture. After receiving number 69, I went through several tests to figure out what bacterium I received. First, I created a slide from my broth by putting a small amount of the unknown broth on to a clean slide and letting it dry for ten minutes. After this, I stained the slide by applying four reagents in order; crystal violet, grams iodine, decolorizer and safranin. From the stained slide, I discovered that this bacterium was gram-negative, which would determine the next couple of tests I would do to identify my unknown bacterium. I began by streaking for confluent growth from my broth culture onto a TSA plate. From the TSA plate, I aseptically transferred a loop

This experiment is about bacterial growth. We will demonstrate a bacterial growth curve using a closed system. Bacterial growth usually takes up to 12-24 hours to get an accurate result so we will be monitoring this growth between two classes. We also used different methods to determine bacterial growth as well as a few different calculations. One way of receiving data is by using a spectrophotometer where we will record the absorption at a given time to create the bacterial growth curve. We also used the plate count method after performing a serial dilution to calculate the actual cell density at different times given. By using this method we can count the population number of the same given and see the maximum cell density

In the medical field which I am going into, it is very important to be able to identify bacteria. By identifying bacteria, we can prevent, diagnose its presence and determine what is the appropiate treatment to treate the diseased caused by them. For example, if a patient is complaining of a sore throat we can take a sample of the throat to determnne what bacteria if any is causing the pain. Once the bacteria has been identified the patient can be prescribed the appropiate antibiotic. Another reason why is so important to identify bacteria and to know its characteristics, is for pharmaceutical companies to come up with medication and to decided the type of vaccines that can be used to counter it.

In this lab experiment, students had to create a growth curve for E. coli. The E. coli growth curve would illustrate the progression of the population of E. coli a set time period. In this case, the growth curve depicted the population of E. coli over a 12-hour period. The growth curve for E. coli was created from the absorbance levels, the optical density(OD), recorded from the spectrophotometer.

The sample appeared a dark pink or close to violet by the naked eye; a

If there is question of the two types of bacterium being located in the specimen then the addition of the counterstain safranin. As the procedure continues alcohol is introduce to the sample to differentiate the Gram-negative and the Gram-positive bacterium with it causing the outer layer of the Gram-negative cells to dissolve allowing the counterstain to remain to mask to crystal violet color making the cells show as pink or red vs. purple. In particular cases of staining of Bacillus, some Gram-positive cells will give a Gram-negative response though they are dead, there can be increasing numbers of Gram –negative cells; this is called Gram-variable. (Tortora, 2014) The procedure relating to staining for observation of Mycoplasmas involve a detailed and specific protocol for success. As previously mentioned, Mycoplasmas have little to no cell wall; the staining process has to be relative to what can be stained for observation. In my research, I found that the use of a specific stain, the Hoechst #33258 dye, is used to illuminate by florescence the DNA of Mycoplasma bacteria so it can be differentiated from the remainder of the sample by the use of a UV filtrated, florescent microscope. (Sciences, 2002) The opportunity of each of the given genera that could cause this particular