Gram Staining

An unknown bacterium was handed out by Dr. Honer. The appropriate tests were prepared and applied. The first procedure that was done was the gram stain. Under a microscope, if the gram stain is purple, the bacterium is gram positive, if the stain is red, it is gram negative. The next test was the fermentation tests for glucose, sucrose and

The Gram stain was used to determine if the bacteria was gram positive or negative. A negative test shows a pink color and a positive test is a purple color. When a bacterium is negative it is because it has an outer membrane and a thin layer of peptidoglycan that is much harder to stain. A positive bacterium has a thick layer of peptidoglycan and no outer membrane that can be penetrated by crystal violet.

The next step of the project included preparing a Gram stain to discover the cell shape, arrangement, and if the bacteria is gram positive or

This experiment was given to us to utilized previous knowledge learned throughout the semester to identify a gram negative unknown bacterium. We had to first learn the difference between a gram negative and a gram positive organism. We started off with doing gram stains to determine whether it was positive or negative. Based on the gram stains, a gram positive stains purple and a gram negative stains pink. A gram positive stains purple because the cell walls is made of a thick peptidoglycan layer and doesn’t

In this experiment, an unknown bacterium was given to each individual student. The main purpose of this lab was to identify the given unknown bacteria going through a series of biochemical tests as one of the gram negative bacteria among six different Gram negative bacteria Escherichia coli, Enterobacter aerogenes, Klebsiella pneumoniae, Proteus mirabilis, Pseudomonas aeruginosa and Salmonella typhimurium. At the very beginning, streaking method; T-streak technique was used to isolate the pure colonies. For the morphological identification of unknown bacteria, Gram Stain Method was done. Biochemical tests that were conducted for the experiment

The purpose of this lab was to identify an unknown microorganism using lab techniques. The importance of identifying microorganisms is essential to the survival of humans, expansion of modern day medicine and improvement of quality of life. In 1884, Hans Christian Gram designed a differential staining technique to identify bacteria that would change the future of microbiology. He give rise to a staining process, known as the Gram stain to differentiate microorganisms into two groups between positive and negative gram staining microorganisms. The Gram stain is essential in a lab technique as it distinguishes the cells based on the physical properties of the individual cell walls, and is almost always the first test preformed to differentiate a microorganism. The identification of weather a microorganism is gram positive or negative can revel the bacteria’s virulence, cell wall structure, resistance to antibiotics, resistance to physical disruptions and so much more. In order to identify the unknown provided, unknown #27, the Gram stain was the first test preformed. After discovering that the unknown bacterium was indefinitely a gram positive microorganism, the vast possibilities were narrowed down. However, In order to more definitively identify the unknown, the next step was to preform biochemical tests. A biochemical test identifies metabolic

8. Discuss a possible mechanism of Gram Staining in terms of differences in structure and chemistry between the walls of gram-positive and gram-negative

Gram staining is a technique used to determine if the bacteria is Gram positive or Gram- negative. Gram staining procedure uses crystal violet stain, iodine moderator, alcohol decolorizer and safarin counter stain. In Gram- negative bacteria the primary stain will be washed out with the decolorizer and it will be stained with the counterstain. Whereas in Gram-positive bacteria the primary stain will not leave the cell wall. This difference comes from difference in the structure of the cell wall that retains the stain.

Crystal violet stains the cell of the bacteria and is placed over the heat fixed slide for one minute then rinsed with H2O. The mordant that binds the stain is gram’s iodine and is recommended to be present on the slide for one minute. Alcohol is used as the decolorizer and is dripped over the recently rinsed slide until the slide runs slightly blue. If the bacterium retains the crystal violet it is due to the thicker peptidoglycan in the cell wall (gram-positive). The bacteria will then be stained with the counterstain safranin for 45 seconds. When crystal violet is not retained in the cell wall of the bacterium it will stain pink (gram-negative). A gram stain was immediately performed with the recently inoculated streak plate. An inoculating loop was used to gather some of the bacteria from an isolated colony. The loop was placed on a new slide and the transferred bacterium to the slide. The slide was dried, heat-fixed, and the gram stain process just described was completed. After microscopic analysis, it was determined the first unknown bacteria was a gram-positive cocci. The second unknown was determined to be gram-negative cocci. With this information a set group of test decided and performed based on the Unknown Bacteria Flow Chart as provided in the lab manual (Pg.) these test and the results are shown in record on the following pages. These are separated for the gram positive and the gram negative

I performed a gram stain on my unknown 7. It appeared to be purple and round shaped. I came to the conclusion that my bacterium is gram-positive, cocci. A gram stain is a differential test. It allows recognizing the difference between two cell walls structures. In a gram-positive cell wall contains a thick peptidoglycan layer covering the plasma membrane (2). The purple staining is retained around the cell

There are numerous reasons why it is essential that gram stain and microscopic examinations are the first step in identifying pathogenic bacteria. Gram stains are an important procedure because it can determine the stain of the cell wall of bacteria sample. It also allows laboratory technicians to classify the bacteria in to either gram positive or negative as well as allowing them to analyse and study the morphology and arrangement of bacteria. Whilst determining the bacteria type and type of gram stain, the test also allows the doctors to prescribe the correct medication and dose and proceed with the correct diagnoses and treatments to eliminate the bacteria present. The gram stain procedure is known to be a very rapid procedure which has many benefits such as quick treatment and stopping the bacteria from spreading in many ways which may be in the environment or inside the human body. This procedure which allows professionals to determine the bacteria is also an inexpensive technique which benefits many individuals as it is affordable.

Gram Staining             Gram Staining is a procedure used to distinguish between gram-positive and gram-negative bacteria, where one of the main differences is the cell wall. Gram-positive bacteria contain multiple layers of peptidoglycans and gram-negative lacks of peptidoglycans in the cell wall. Overall, is a short procedure that consists of the following steps: first apply the primary stain (crystal violet), second apply the mordant (Gram’s iodine), third apply decolorizing agent (ethanol or ethanol acetone) and finally apply secondary stain (safranin). Another purpose of gram staining is to determine the bacteria’s morphology.

Your Project 4 is description of the process or description of how something works. In other words, you will be describing step by step how Gram Staining characterizes the samples into Gram-negative or Gram-positive bacteria using the stains.

Purpose: To understand the difference between Gram positive and Gram negative bacteria. We also used this lab to examine our mixed culture, which had been Gram stained, under the microscope.

This report represents my individual effort. I did not receive or offer aid to anyone when performing this assignment, nor did I plagiarize any material.