In this experiment, a series of biochemical test and API 20 E test are carried out to identify the unknown bacterial species provided. MacConkey agar, a selective and differential medium which is designed to isolate and differentiate the gram negative enteric bacteria. Bile salts and crystal violet inhibit the growth of gram positive organisms. Lactose provides a source of fermentable carbohydrate, allowing for differentiation of lactose fermenting bacteria from lactose non-fermenting gram negative bacteria. It uses for differentiate gram negative bacteria between phenotypes with mutations that confer varying abilities to ferment particular sugar. The medium surrounding gram-negative bacteria will show a change in colour. Neutral red in MacConkey …show more content…
The bacteria ferment lactose, then cause the pH of the media agar to drop and resultant change in pH is detected by neutral red. The neutral red is absorbed by the lactose fermenting bacteria and appear as bright pink to red on the MacConkey agar. The strong lactose fermenting bacteria produce resulting in a pink halo in medium while the weaker growing on MacConkey agar will still appear pink to red but will not be surrounded by a pink halo in the surrounding medium. The gram-negative bacteria that grow but do not ferment lactose appear as colourless on MacConkey agar plate. The agar surrounding the bacteria remains transparent. Lactose can be replaced in the medium by other sugars and the abilities of gram-negative bacteria to ferment these replacement sugars is detectable in the same way as lactose …show more content…
This test usually used to differentiate catalase positive bacteria such as Staphylococcus spp. and the Micrococcus spp. from catalase negative Streptococcus and Enterococcus spp. Bacteria lacking the cytochrome system, also lack the catalase enzyme and are unable to break down hydrogen peroxide, into oxygen and water and are catalase negative. The effervescence resulting from production of oxygen gas clearly indicate a catalase positive result. From the experimental observation, the unknown bacteria provided shows positive test with gas bubbles formation indicating the presence of
Table 6 shows the results of the biochemical tests. The isolate can obtain its energy by means of aerobic respiration but not fermentation. In the Oxidation-Fermentation test, a yellow color change was produced only under both aerobic conditions, indicating that the EI can oxidize glucose to produce acidic products. In addition to glucose, the EI can also utilize lactose and sucrose, and this deduction is based on the fact that the color of the test medium broth changed to yellow in all three Phenol Red Broth tests. These results are further supported by the results of the Triple Sugar Iron Agar test. Although the EI does perform fermentation of these three carbohydrates, it appears that this bacterium cannot perform mixed acid fermentation nor 2,3-butanediol fermentation due to the lack of color change in Methyl Red and Vogues-Proskauer
One bacterium was gram negative. It underwent four different tests. These tests were the EMB test (Eosin Mehylene Blue), the Sulfur Indole Motility (SIM) test, the Urease test, and the Simmon’s Citrate Utilization test. The EMB test checks for a bacteria’s ability to ferment lactose. This test is accomplished by placing the bacteria on Eosin Methylene Blue agar. The agar is selective for gram negative bacteria and those bacteria that can ferment lactose will have colored growth, usually a metallic green sheen.
In this lab project, the microbiology students were given 2 unknown bacteria in a mixed broth each broth being numbered. The goal of this project is to determine the species of bacteria in the broth. They had to separate and isolate the bacteria from the mixed broth and ran numerous tests to identify the unknown bacteria. The significance of identifying an unknown bacteria is in a clinical setting. Determining the exact bacteria in order to prescribe the right treatment for the patient. This project is significant for a microbiology students because it gives necessary skills to them for future careers relating to clinical and research work.
They can be found anywhere and identifying them becomes crucial to understanding their characteristics and their effects on other living things, especially humans. Biochemical testing helps us identify the microorganism present with great accuracy. The tests used in this experiment are rudimentary but are fundamental starting points for tests used in medical labs and helps students attain a better understanding of how tests are conducted in a real lab setting. The first step in this process is to use gram-staining technique to narrow down the unknown bacteria into one of the two big domains; gram-negative and gram-positive. Once the gram type is identified, biochemical tests are conducted to narrow down the specific bacterial species.
These labels indicated the lactose solution that was be placed into the mini-microfuge tubes. The varying lactose ph solutions were obtained. The four miniature pipets were then used, (one per solution,) to add 1mL of the solution to the corresponding mini-microfuge tubes. When this step is completed there were two mini-microfuge tubes that matched the paper towel. Then, once all of the solutions contained their respective lactose solutions, 0.5mL of the lactase enzyme suspension was added to the first mini-microfuge tube labeled LPH4 on the paper towel, and 4 on the microfuge tube. As soon as the lactase enzyme suspension was added to the mini-microfuge tube, the timer was started in stopwatch mode (increasing.) When the timer reached 7 minutes and 30 seconds, the glucose test strip was dipped into the created solution in the mini-microfuge tube for 2 seconds (keep timer going, as the timer is also needed for the glucose strip. Once the two seconds had elapsed, the test strip was immediately removed, and the excess solution was wiped gently on the side of the mini-microfuge tube. The timer was continued for 30 addition seconds. Once the timer reached 7:32 (the extra two seconds accounting for the glucose dip), the test strip was then compared the glucose test strip color chart that is found on the side of the glucose test strip
The purpose of this laboratory is to learn about cultural, morphological, and biochemical characteristics that are used in identifying bacterial isolates. Besides identifying the unknown culture, students also gain an understanding of the process of identification and the techniques and theory behind the process. Experiments such as gram stain, negative stain, endospore and other important tests in identifying unknown bacteria are performed. Various chemical tests were done and the results were carefully determined to identify the unknown bacteria. First session of lab started of by the selection of an unknown bacterium then inoculations of 2 tryptic soy gar (TSA) slants, 1 nutrient broth (TSB), 1 nutrient gelatin deep, 1 motility
Phenotypic methods of classifying microorganisms describe the diversity of bacterial species by naming and grouping organisms based on similarities. The differences between Bacteria, Archaea and Eukaryotes are basic. Bacteria can function and reproduce as single cells but often combine into multicellular colonies. Bacteria are also surrounded by a cell wall. Archaea differ from bacteria in their genetics and biochemistry. Their cell membranes are made with different material than bacteria. Just like bacteria, archaea are also single cell and are surrounded by a cell wall. Eukaryotes, unlike bacteria and archaea, contain a nucleus. And like bacteria and archaea, eukaryotes have a cell wall. The Gram stain is a system used to characterize bacteria based on the structural characteristics of their cell walls. A Gram-positive cell will stain purple if cell walls are thick and a Gram-negative cell wall appears pink. Most bacteria can be classified as belonging to one of four groups (Gram-positive cocci, Gram-positive bacilli, Gram-negative cocci, and Gram-negative bacilli) (Phenotypic analysis. (n.d.).
mutans was problematic due to its difference with Bergey’s Manual result for the catalase test. However, after comparing it with a peers results, it seems very possible that the strain we are working with varies from the strain used in Bergey’s. Bacteria possess the ability to develop varying phenotypes within the same species due to frequent mutation and horizontal gene transfer. Therefore, it is possible that the results obtained in our lab may vary from those provided in Bergey’s Manual. Arriving to the conclusion that the Gram negative bacteria was Klebsiella pneumoniae was much more direct. Using Bergey’s Flowchart for identification, the bacteria shared the test results and had a similar shape and
* For the yeast culture ; * 6 g of dried active bakers yeast ; 6 sugars (enough for 6 yeast cultures) in this investigation. sugars used were: Glucose, Fructose, Dextrin, Ribose, Galactose and Sucrose. 600 ml of distilled water. 6 Conical flasks with air blocks (in this instance cotton wool).
A scientist named Christian Gram invented a technique called gram staining by which is colorized that is separated into two groups Gram positive and Gram negative. In bacteria most have rigid cell walls in which is accountable for the shape of the organism. Within the cell wall of the bacteria it identifies whether the bacteria is gram positive or negative. In the cell wall there a lot of difference that determines the bacteria is gram is positive or negative for example the thickness and the amount of peptidoglycan later presences or absence of outer membrane and teichoic acids. Where gram positive have two later and negative has three layers. Gram positive the cell wall is a single layer, primarily composed of peptidoglycan, does not contain outer membrane and contains negatively charged teichoc acids, this result of a blue color indicator. For gram negative is more complex that the Gram positive, its membrane lies outside of th...
I identified the genus and species of an unknown bacterial culture, #16, and I applied the following knowledge of morphologic, cultural and metabolic characteristics of the unknown microorganism according to the laboratory manual as well as my class notes and power point print outs. I was given an incubated agar slant labeled #16 and a rack of different tests to either examine or perform myself; the tests are as follows: Gram Stain; Nutrient Gelatin Test; Carbohydrate Fermentation; Dextrose, Lactose and Sucrose; IMVIC tests; Citrate, Indole, Mythel-Red and Vogues Proskauer test; as well as a Urease and TSI Test. Materials and Methods/Results Upon receiving the Microorganism (M.O.) #16, I prepared a slide by cleaning and drying it. Then, using a bottle of water I placed a sterile drop of water on the slide and used an inoculating loop, flame sterilized, I took a small sample of the unknown growth in my agar slant and smeared it onto the slide in a dime sized circle and then heat fixed it for ten minutes.
This lab has two sections. The first section deals with fermentation. The purpose of the fermentation lab is to alter 5 different independent variables (temperature, acid ph, alkali ph, enzyme concentration, and substrate concentration), to learn about their effects on the ongoing process of fermentation.
While Pasteur was at Lille, a local distiller sought help controlling the fermentation of beet sugar. Pasteur realized that fermentation was not a simple chemical process but that living organisms were involved. This led him to discover that fermentation, infection, and spoiling were the result of microbes. The first paper he published discussed lactic acid and it’s role in souring milk. He spent numerous years studying microbes and proving that they do not originate from within matter, but that they come in from the outside. He eventual...
Leboffe, M. J., & Pierce, B. E. (2010). Microbiology: Laboratory Theory and Application, Third Edition 3rd Edition (3rd Ed.). Morton Publishing
There were five test solutions used in this experiment, water being the control, which were mixed with a yeast solution to cause fermentation. A 1ml pipetman was used to measure 1 ml of each of the test solutions and placed them in separated test tubes. The 1 ml pipetman was then used to take 1ml of the yeast solution, and placed 1ml of yeast into the five test tubes all containing 1 ml of the test solutions. A 1ml graduated pipette was placed separately in each of the test tubes and extracted 1ml of the solutions into it. Once the mixture was in the pipette, someone from the group placed a piece of parafilm securely on the open end of the pipette and upon completion removed the top part of the graduated pipette.