Unknown 12 Lab Report

The Unknown Bacteria 36/Bacteria # 2 on a TSA plate was examined by the naked eye and under a dissecting microscope. Bacteria # 2 was approximately 3 - 4 mm in diameter. They were circular in form with an entire margin and a flat elevation. The colonies were rough (granular), translucent, and white brownish color with black granules. The Gram stain resulted in a Gram negative rod. After the Gram stain was completed, the bacteria were streaked on an Eosin -Methylene Blue Agar plate and an Enterotube II was inoculated.

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)

In a laboratory setting, it often becomes necessary to identify an unknown organism. In this experiment, researchers classified an unidentified bacterium based on its physical structure, colony morphology, optimal conditions and metabolic properties. A Gram stain using crystal violet, iodine, and safranin and a simple stain using methylene blue characterized the organism’s cell wall. Cultural behavior was classified by inoculating the organism onto nutrient agar and incubating it at 37° C for 48 hours, and observing its behavior, as well as using SIM medium to test for motility. Optimal growth temperature was

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

Bacteria groups or species can be differentiated by the fermentation patterns. The end-product of carbohydrate fermentation is an acid or acid with gas production and is dependent on the organism involved in the fermentation process. The carbohydrate fermentation tests detect if an organism is able to utilize glucose, lactose and sucrose. Phenol red is used as a pH indicator because it can indicate a change in pH when acid products are formed. Bacteria can utilize certain sugars resulting in an alkaline by-product which changes the color of the carbohydrate broth from red to yellow. Bubbles trapped within the Durham tube indicate the production of gas. The Phenol red carbohydrate fermentation tests determine that my organism E. coli can utilize glucose, lactose and sometimes sucrose but can only produce gas in glucose and lactose. (Phenol red carbohydrate fermentation lab

The importance of identification of a certain microorganisms can range between a life threatening diseases to a creation of certain antibiotic. Understanding the principals of living microbes and identifying my unknown bacteria through numerous biochemical and metabolism tests, with the outmost confidence, Proteus vulgaris had the precise qualifications. The point of this report is to further explore the identification of my unknown bacteria by revealing the results of the experiments and comparing them to the other six known bacteria: Micrococcus luteus, Staphylococcus aureus, Staphylococcus epidermidis, Alcaligenes faecalis, Escherichia coli, and Proteus vulgaris that were used in the lab, as well as comparing and

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

After confirming that the bacteria is gram negative, the following test that will need to be done is the oxidase test. This is done by adding a few drops of oxidase reagent to a swab that has collected a single colony from the TSA plate. If the swab changed to a purple color within 5 seconds, this indicated that the organism is oxidase positive. The organism that was tested was positive for oxidase.

The oxidase reagent contains a reducing agent that changes to a purple color when it becomes oxidized. Since P. aeruginosa is the only bacterium that contains cytochrome c oxidase, it will be the only oxidase-positive bacterium. Materials & Methods For the oxidase test, we had to obtain a new reagent dispenser and crush the glass ampule inside the dispenser. With a sterile swab, we then obtained a small amount of each bacteria individually from an agar slant.

Gram staining differentiates between Gram positive and Gram negative bacteria and provides cell morphology. From this, pink bacilli were observed, providing a Gram negative result. Thus the unknown was narrowed down to E. coli and P. aeruginosa. Next was the Fluid Thioglycollate Media (FTM) which consists of a sugar broth and determines the oxygen requirements for the unknown. Since the turbidity was observed at the top of the tube, thus the unknown was an aerobe, just like P. aeruginosa and not E. coli which is a facultative anaerobe. Then a Durham tube with a glucose broth was used to determine whether the bacterium produces acid and gas from carbohydrate fermentation. Since only a red broth with some turbidity at the top was observed it could not have

The Catalase tests involves exposing the colony of interest to hydrogen peroxide to check for the presence of the enzyme Catalase. If the bacteria contain the enzyme, exposure to hydrogen peroxide will trigger the breakdown of it by Catalase as a defense mechanism against the harmful substance. Catalase test positive genera include Bacillus, Micrococcaceae, and Staphylococcus, while Clostridium and Streptococcaceae test negative (Holbrook and Leicht, 2015). The second test administered to gram-positive bacteria is the Mannitol Salt Agar (MSA) test. This test involves observing growth of the bacteria on the MSA medium, which contains very high amounts of sodium chloride. The only strain capable of growth is Staphylococcus, which causes the medium to change in color from red to yellow, indicating fermentation of the

When cultured on a Mannitol Salt Agar plate, we looked to observe if the isolate fermented mannitol. It was determined that the isolate ferments mannitol because of the yellow colonies that grew. The next test in this battery tested the presence of Catalase which is an enzyme that protects cells from damage by hydrogen peroxide by breaking it down into water and oxygen. The oxidase test which determines the presences of cytochrome oxidase determines if a bacterium can use oxygen as an energy source. The isolate tested positive for catalase but negative for oxidase. The final test to be conducted was to observe the possible lysis and degree of lysis caused by the unknown isolate. On a BPA plate, the unknown isolate lysed the surrounding red blood cells

Only the Gram positive organisms were put through the starch test, as testing the Gram negative organisms would not have helped with identifying the unknown organism. Proper inoculation techniques were used to transfer the Gram positive organisms onto the starch plate in a straight line, and then the plate was incubated. The following week, after incubation, the plate was flooded with Gram’s iodine and was left to sit for ten minutes. Gram’s iodine indicated the presence of starch by forming a starch iodine complex that turns blue-brown or black. After pouring the excess iodine off, the plate was set on a white paper to analyze. A positive test with amylase present would present itself with a halo of clearing around the cell

Catalase Test: After doing the catalase test, as we put drops of 3% Hydrogen Peroxide, it starting bubbling on the microscope slide which indicates a positive result. This means that the unknown bacteria has the catalase enzyme present, which decomposes hydrogen peroxide into water and oxygen. (Needs Editing)

Staphylococcus aureus is a gram positive coccus found in the human respiratory tract and on the skin. It is a facultative anaerobic organism that appears as grape-like clusters under a microscope, and has large, round, golden-yellow colonies with hemolysis, when grown on blood agar plates.