Project: Streak Technique

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.

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)

This conclusion can be made because after gram staining it showed dark purple cocci, meaning it is Gram-positive. Then once a catalase test was done, bubble formation was absent and when inoculated into the Bile Esculin tube and incubated the agar didn’t turn black meaning it was negative. When it comes to sample B, it is concluded that it is Escheria coli. The conclusion was made due to the gram staining showing red rods, meaning it was Gram-negative Then after the SIM test was left at Room temperature for a day, no indication of sulfur reduction was present due to the tube still being clear and once the Kovacs reagent was added.

My unknown organism #11 is Escherichia coli (E. coli). E. coli belongs to the family Enterobacteriaceae. E. coli is Gram-negative, facultative anaerobe, and rod-shaped bacteria (bacillus). [1]

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.

I identified Citrobacter freundii, the gram negative rod, by running a series of tests. I began with the Phenol Red Lactose tests, which tests if the organism contains various enzymes that determine if it can ferment lactose. The broth turned yellow after it was incubated, indicating that the lactose was fermented to acid, and there was also gas present in the Durham tube. Since the Phenol Red Lactose Test was positive, I then ran the Phenol Red Sucrose test, which tests if the bacteria contain different enzymes that determine if sucrose can be fermented. After incubation, the broth was yellow, indicating that sugar was fermented to acid, and there was also gas present in the Durham tube. Next, I ran the Sulfide Production, Indole Formation, Motility test, but I was only testing for Hydrogen Sulfide Production to differentiate between the organisms Citrobacter freundii and Enterobacter aerogenes. This test detects if the organisms can metabolize sulfur into hydrogen sulfide, which is revealed by the formation of ferrous sulfide that causes blackening around the growth. The test also reveals if the organism can break tryptophan into indole or migrate away from initial stab area. After incubation, the agar slant was completely black, indicating that the organism produces hydrogen sulfide and is motile proving that it was Citrobacter

The test showed a clear zone around the colonies thus determining that the bacteria can break down starch meaning it was a positive result. With a positive starch hydrolysis result the next task was to perform a VP. The results from this test came back negative because there was no color change in the broth. My next step was to check for a swollen cell. I found that the cell was swollen looking from the spore stain slide.

Unknown lab report# 24 Introduction Microbiology is a study of organisms that surrounds us every day. It requires an educational understanding to identify organisms, and the ability to distinguish different bacteria’s. In applying the learning process of the different bacteria’s, unknown bacteria samples are given to be studied and identified.

The main objective was to identify an unknown organism by utilizing skills we learned in our labs this semester. The purpose was to attain the possible identity of the unknown organism by actually performing biochemical tests and staining techniques we learned in lab. After performing and analyzing the results, we were able to use Bergey’s Manual of Systemic Bacteriology as a guideline to narrow down the genus of our organism test by test.

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 project’s purpose as a whole was to receive an unknown bacteria and figure out what it is; One can figure this out by doing a series of tests. These tests include but are not limited to: gram stains, capsular stains, MacConkey agar plates, SIM, KIA, and UREA tubes, Catalase and Oxidase tests, Methyl Red and Voges-Proskauer test, and many, many more. Although that was just naming some of the tests one can do, what they are and how they’re done are further explained in the methods and reports section. Although there were many tests I was able to do, I was limited to an extent. I only had a few weeks to work on the project, and there were some unavailable tests I was unable to do.

When checking the results, H2S was negative, there were no black precipitants in the tube, and the organism was motile. After recording those results, I went to the hood to add Kovoc’s reagent to the SIMs and waited for about 30 minutes before observing to get the results, and it came out to be negative for indole as well. At this point, only one organism matched every result that I received during all my tests, I decided to do my confirmation test. I did Methyl Red and Voges-Proskauer tests for my confirmation test. After inoculating the MRVP broth and incubating it at 37oC for 120 hours, I took my separated samples to the hood and added in the Methyl Red in one tube and reagent A then B in the other tube, I mixed it and checked in on both tubes after every 10 minutes. About 45 minutes later it was clear what the results were, negative for methyl red and positive for Voges-Proskauer. That confirmed that my unknown O17 was Enterobacter

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.

The conclusion that was made from this experiment was that as the streaking is completed the consistency as well as the concentration degrees allowing for a more accurate identification of the individual particles. The results lead me to this conclusion because as the streaks were completed the

Determination of the bacteria being a lactose fermenter or non fermenter is done through the growth on the MacConkey agar. Knowing this allow for the student to perform the necessary tests to determine which lactose fermenter was present in the sample. The Indole test allows for the determination of whether the unknown bacteria is Escherichia coli because this genus and speices is the only lactose fermenter that will produce a positive result here. Moving onto the Methyl red test this indicates glucose fermentation, more specifically microbes that produce mixture of acids as a result of fermentation. The Voges-proskauer tests for glucose fermentation, specifically organisms whose acid is converted to acetoin. The Citrate test differentiates an organism’s ability to use citrate as its only carbon source. The urea broth culture detects the enzyme urease, which allows break down of urea producing acid, which causes a noticeable change in color. The final test is the motility test to determine if the bacteria has the capacity of movement beyond the point of