Unknown Lab Report Abiola Oyewumi March 16, 2015 Unknown #16 Abstract An experiment was conducted to determine which of the following unknown bacteria was in test tube number 16: Escherichia coli, Enterobacter aerogenes, Klebsiella pneumoniae, and Salmonella typhimurium. Biochemical tests were used to help identify the unknown bacteria. The Citrate test, Urease test, Triple Sugar Iron Agar test, Voges-Proskauer test, and Methyl Red test were the biochemical tests used in this experiment. The T-Streak method was also used to ensure that pure colonies were created. The results of the biomedical test concluded that the unknown bacteria number 16 was in fact E. aerogenes. Introduction Gram-negative and Gram-positive bacteria are similar but also …show more content…
The reason the Gram-negative bacteria stains red or pink is because of the peptidoglycan layer (Leboffe and Pierce 105). Unlike Gram-positive bacteria, Gram-negative bacteria have a very thin peptidoglycan layer. The Gram-positive bacteria thick peptidoglycan layer is able to hold the primary stain, crystal violet, which causes it to stain purple (Bacterial Morphology). When the primary stain is placed on the Gram-negative bacteria, the thin peptidoglycan layer is not able to preserve the primary stain and is washed away throughout the gram stain procedure. Gram-positive bacteria contains teichoic acid which give the bacteria a negative charge (Bacterial Morphology). Gram-negative bacteria also have a negative charge but get the charge from lipopolysaccharides (Bacterial Morphology). For this experiment, biochemical tests were utilized to help determine which of the following four bacteria were in the unknown test tube number 16: E. coli, E. aerogenes, K. pneumoniae, and S. typhimurium. The unknown bacteria was also inoculated and placed on a TSA plate using the T-Streak method to verify that isolated colonies could be obtained. The biochemical tests that were used were the Citrate test, Methyl Red test, Voges-Proskauer test, Urease test, Sulfur Indole Motility test, and Triple Sugar Iron Agar test. The biochemical tests helped differentiate …show more content…
The medium did not change color after the Kovac reagent was added. Thus, the microorganism was not able to reduce sulfur to hydrogen sulfide (Leboffe and Pierce 202). The lack of blackening in the medium confirms the negative results. The organism tested negative for indole production. If indole was produced, dimethylaminobenzaldehyde (DMABA), which is in the reagent, would reacts with any indole that is present in the media (Leboffe and Pierce 202,203). Therefore it can be concluded that indole wasn’t produced and that the organism did not possess tryptophanase and could not hydrolyze tryptophan into pyruvate, ammonia, and indole. However, the organism tested positive for motility. After the incubation period, the growth of the organism radiating in all directions in the test tube (Leboffe and Pierce 203). The stab line was no longer visible. The positive motility results imply that the microorganism is cable of moving
Last test, inoculation of phenylalanine agar is used to determine if phenylalanine deaminase oxidizes phenylalanine into phenylpyruvic acid and ammonia. Sixth test, is a Multiple Test Media used to determine the physiological characteristics of unknown #398. First test, Inoculation of Kligler 's Iron agar was used to determine the production of hydrogen sulfide from cysteine and fermentation of glucose and lactose. Last test, inoculation of litmus milk is used to determine the fermentation of lactose, casein, lactalbumin, and
The purpose of this lab report is to employ a myriad of skills, tools and, methods learned throughout this semester to perform the appropriate tests for the identification of the assigned unknown bacteria. Add more background information here!!! The most important tools and techniques used during this identification include aseptic technique, microscopic examination and, the use of selective and differential media. Aseptic technique is an important tool for microbiologists. It is imperative that aseptic technique is maintained throughout the length of any test to avoid any cross-contamination that may lead to inaccurate results.
I expect to learn the biochemical differences in bacteria from this lab. Also, how to identify different species of bacteria. Material & Methods For the first day of the practical, an unknown specimen was provided
Another hypothesis made was that the bacteria would glow with the addition of the sugar arabinose. All three of the objectives seem to go hand in hand. The lab began by inserting transformation
Unknown Paper I Introduction This lab is a presentation of lab tests performed to finalize a conclusion based on results to identify the given unknown bacteria. The unknown bacteria was identified based on lab test results in the table provided in class for the possible unknown bacteria. The unknown bacteria identified as #36, and based on the lab tests is Enterobacter II Materials and Methods Catalase Test- this test determines whether bacteria have the enzyme catalase which catalyzes the breaks down hydrogen peroxide.
It is necessary to understand what each test reveals about the unknown. Citrate tests are performed in order to distinguish between different enteric bacteria by seeing which can use citrate as the sole carbon source. MR/VP are tests that are used to distinguish between different types of fermentation either mixed acid or butanediol and test for the production of acetoin. H2S production is used to determine whether or not the bacteria can produce hydrogen sulfide. Mannitol high salt testing is done in order to determine if the bacteria is salt tolerant and can ferment mannitol.
The unknown bacteria was then tested on multiple selective and differential media. Growth was present on the MacConkey Agar and the colonies were the same color as the plate, which told me my bacteria was gram negative and did not ferment lactose. There was no growth on the Mannitol Salt Agar, and this told me the unknown was not salt tolerant and did not
By Gram staining alone, it was safe to eliminate the three Gram positive bacteria that could have been assigned: S. epidermidis, M. luteus, and B. megaterium. The second step was to streak plate Unknown #10 to observe its macroscopic
The second ½ of the organism was used for gram staining. The gram stain method was performed on the unknown organism per lab manual page 42 and two gram stain reactions were identified. Organism B was gram positive cocci in grape like clusters. Because organism B was positive I could eliminate Escherichia coli, Enterobacter aerogenes and Proteus vulgaris because these bacteria would be rod shapes. Organism A was gram negative pink rod shaped and because of gram positive morphology I could eliminate Staphylococcus aureus, Streptococcus lactis and Bacillus subtilis.
After a gram stain was done unknown #257 was identified as a gram positive organism because when observed under the microscope the organism appeared purple with cocci in clusters. The organism was also catalase positive which means that it produced enzyme catalase and bubbled when hydrogen peroxide was added to it. Three test were conducted based on the result of the gram staining procedure. Blood agar with a Novobiocin disk was chosen as well as DNase (DNA) and Mannitol Salts (MSA) agar. The Blood agar is a bright red, opaque plate and the streaking or the inoculation technique was a modified streaking for isolation with a heavy quadrant one.
Three bacterial cultures were received from laboratory staff. The colonies that cultures were grown from came from ligations and transformations that were prepared by the laboratory staff. The cultures prepared during the ligation and transformation steps were unusable due to unsuccessful ligation. Two colonies were taken from an LB/kanamycin/IPTG plate. One that fluoresced green under UV light, and one that did not fluoresce green under UV light.
Because of the very nature of bacteria, it is important to keep a sterile environment during experiments; aseptic technique is vital. Aseptic technique involves an especial attention to cleanliness in the experiment’s environment, and minimum exposure to anything that might
Aseptic technique was initiated at the beginning of this experiment by cleaning the work surface with disinfected wipes. Personal protectives equipment was also worn. The material utilized in this experiment was: S. epidermidis culture broth, sterile cotton swab, streak plate, forceps in 70% alcohol, a lit tea light, and the three antibiotic disks (novobiocin, gentamicin, penicillin). The first step, I divided a plate into three quadrants and labelled them with the different antibiotic names. Using the lit tea light, like a bursen burner, I flamed the mouth of the S. epidermidis culture.
After experiment on microscope under oil immersion, I learned that my Unknown is gram positive. Under the lens, the bacteria appears in purple color. Its morphology is cocci arranged in cluster. However, during decolorizing process, I put too much alcohol to the crystal violet-iodine complex making the color overly removed. That led to the result of my gram positive has slightly redish
Structurally it is rod-shaped and it falls under gram-positive bacteria since it doesn't have an outer cell membrane. It lacks spore formation capability unlike most bacterial and it can make ATP by the process of aerobic respiration should there