Gram Staining Experiment

Improved Essays
Introduction Gram staining is a method commonly used to determine the chemical make up of the cell wall of bacteria. The cell wall can stain either positive or negative, depending on its chemistry.The aim of this experiment. Gram staining was the first differential technique used and still in use to make microscopic vision of bacteria clearer while also sub-divides the bacteria into two major groups: Gram-positive and Gram –negative. This experiment should help us describe how Gram staining affects the different cell walls of the different types of bacteria, based on their structural and biochemical differences. Different bacteria have different cell walls that react differently to the staining and de-colourisation procedure of Gram staining. …show more content…
If the bacteria stains positive it will retain a purple/blue color. If the bacteria stains negative, the bacteria will not retain the purple/blue color, but rather have a pinkish/red color.This method can also be useful in detecting pathogens from suspected specimens that need testing. The dyes used are not only used for Gram staining but extensively used to highlight structure of many biological specimens such as tissues and cells. Gram staining was developed in Berlin, in 1884, by the Danish scientist Hans Christian Joachim Gram. He studied at the University of Copenhagen where here turned as a Professor of Medicine. Gram staining is based on the ability of the bacteria's cell wall to retain the stain colour. Gram-negative bacteria do not have the ability to keep the stain colour of Crystal Violet and Gram's Iodide when washed with alcohol, while the Gram-positive bacteria, when washed with alcohol, causes their cell wall to shrink and traps the stain colour and therefore remains purple. Gram-negative bacteria are finally stained with or Safranine and that is how they obtain a pink …show more content…
If the bacteria stains negative, the bacteria will not retain the purple/blue color, but rather have a pinkish/red color. From my result in Fig 1 below, under the microscope,the bacteria stain positive and retain a purple/blue color. Fig. 1.Gram-positive bacteria appeared purple/blue color under the microscope. A typically gram positive reaction exhibited by Staphylococcus aureus. These organisms characteristically retain the primary dye, usually crystal violet,and appear dark purple in colour.

DISCUSSION All bacteria's cell wall contain peptidoglycan (murein), a molecule unique to bacteria.The cell wall of Gram-positive bacteria is made up of peptidoglycan (murein), a periplasmic space and an inner plasma membrane. The cell walls of Gram-positive bacteria binds with the Crystal Violet stain and thus they become purple.Gram-negative bacteria have many thin layers consisting of an outer membrane made of lipopolysaccharides and protein, periplasmic space, peptidoglycan and aninner plasma membrane. Lipopolysaccharides (LPS) is an endotoxin and can be harmful to organisms infected with Gram-negative bacteria . This outer layer of Lipopolysaccharides is dissolved by the alcohol during Gram staining so the cell wall loose the dye like the Crystal Violet ( 3

Related Documents

  • Improved Essays

    Gram Stain Lab Report

    • 965 Words
    • 4 Pages

    Each one of these test are different and they will give a positive or negative feedback which is how we will know which bacterium I have. A gram stain is one of the most use stain in microbiology. The purpose of a gram stain is to divide microorganisms into gram positive or gram negative. In this procedure you will use Crystal violent, Iodine, Acetone, and Safranin. You use different dyes because Gram negative microorganisms have a higher lipid content and it’s soluble in acetone whereas gram positive microorganisms are less permeable after acetone and the crystal violet-iodine becomes trap inside the cells.…

    • 965 Words
    • 4 Pages
    Improved Essays
  • Improved Essays

    Gram Staining Test

    • 836 Words
    • 4 Pages

    Gram staining was used to distinguish the unknown microbes between gram-positive microbes from gram-negative microbes. Gram-positive microbes contain a thick peptidoglycan with only one outer cell membrane, thus dying the microbes dark purple. Gram-negative microbes contain a thin peptidoglycan with an outer and inner cell membrane, dying the microbes pink when a gram stain test is done. Microbes A and C were gram- positive because of purple dye seen under the microscope. Microbe B was a gram-negative because of the light pink dye seen under the microscope.…

    • 836 Words
    • 4 Pages
    Improved Essays
  • Superior Essays

    Gram Catalase Test Report

    • 1163 Words
    • 5 Pages

    It is also called differential staining because it differentiates among bacteria and can be used to distinguish between them based on the differences of cell wall structure. There are two major groups of bacteria, the gram positive staining cells and gram negative staining cells. In this procedure, the bacteria are first stained with crystal violet “basic stain”, and then treated with adding a mordant, iodine, which fixes the stain inside the cell. The stained cells are washed with a decolorizing agent, alcohol and then counterstained with…

    • 1163 Words
    • 5 Pages
    Superior Essays
  • Great Essays

    Mannitol Salt Agar

    • 1936 Words
    • 8 Pages

    As explained by our textbook, “the chemical composition of the cell wall helps to differentiate major types of bacteria” (Tortora, Funke, and Case 84). The two main types of bacteria are gram positive and gram negative. Their cell walls are composed of peptidoglycan. The peptidoglycan is a chain of repeating disaccharide held together by polypeptides. The disaccharide…

    • 1936 Words
    • 8 Pages
    Great Essays
  • Improved Essays

    Microorganisms

    • 1207 Words
    • 5 Pages

    The use of multiple dyes allows the viewer to identify gram negative and gram positive bacteria based on whether it’s pink or purple, respectively. This occurs because of the chemical differences in these two types of bacteria; gram negative bacteria has a thin layer of peptidoglycan in the cellular membrane and an outer membrane and the gram positive bacteria has a thick layer of peptidoglycan in the cellular membrane and lacks an outer…

    • 1207 Words
    • 5 Pages
    Improved Essays
  • Improved Essays

    This technique is used because the gram negative and gram positive bacteria both have different cells wall structures and also respond differently depending on which type of antibiotic they are given. For example, penicillin which is a type of antibiotic will prevent the synthesis of the cell wall in gram positive bacteria however will not work in gram negative bacteria. Penicillin can be used to treat many different infections such as skin infections. Penicillin is an antibiotic that works against gram positive bacteria as it prevents the peptidoglycan from being formed. Daptomycin is another antibiotic which is used against gram positive bacterial infections.…

    • 1140 Words
    • 5 Pages
    Improved Essays
  • Improved Essays

    MSA also contains mannitol, which allows differential identification because an indicator detects acid produced by the fermentation of mannitol (4). MacConkey agar, which is media containing crystal violet and bile salts inhibits Gram positive bacteria (5). The media is also differential since the fermentation of lactose is detectable on MacConkey agar by pH indicators. Eosin Methylene Blue agar (EMB) contains chemicals that inhibit Gram positive growth and can identify lactose and sucrose fermentation through the previously described pH detection (3,5). Sometimes, media is developed to identify specific organisms.…

    • 1018 Words
    • 4 Pages
    Improved Essays
  • Superior Essays

    Microorganism Lab Report

    • 1710 Words
    • 7 Pages

    The isolated colonies of the bacteria appeared to have grown and they were approximately 0.2 cm average in length. When I observed their visual appearance they were blurred Wight in color with a transparent slime layer placed on top of the white dotes. After taking notes on the physical appearance of the bacteria’s, a gram stain was conducted on the isolated bacterial sample. The stain process is extremely essential because it separates the bacteria in two groups of gram positive and negatives bacteria’s .in addition, the gram stain shows the color, shape, size, and morphology of the bacteria. In order to narrow our search for unknown microbe, acid fast, spore and capsule stain were…

    • 1710 Words
    • 7 Pages
    Superior Essays
  • Improved Essays

    The Lysine Iron Agar (LIA) black cap tube will be used to test decarbonation lysine, if positive for decarbonation it will have a purple slant and if negative it will be a darker red color. The LIA tube will also be used to test decarboxylate lysine, which will help us distinguish bacteria that will produce hydrogen sulfide from those who cannot. If positive for decarboxylate lysine it will have a purple butt, and if negative it will have a yellow butt. The Sulfide Indole Motility (SIM) blue cap tube is a semisolid agar and it is also used to determine sulfide production, indole formation and motility in Gram negative bacteria. We will be adding a couple of drops of Kovacs reagent following the incubation of the unknown organism.…

    • 1262 Words
    • 6 Pages
    Improved Essays
  • Improved Essays

    Observe each slide under the microscope, determining whether the bacteria are gram-positive which is stained purple or gram-negative which is stained red. Results: Through the process of the experiment, e. coli was determined to be gram-negative and S. aureus was gram-positive. By looking through the microscope at the positive staining, the appearance of the cell seemed to be colored by the dye and the background was not stained. The crystal violet made the gram-positive a thick purple layer, which made it easier to see looking through the microscope. When looking at the negative staining, the appearance of the cell seemed clear and colorless, or a faint pink color.…

    • 1370 Words
    • 5 Pages
    Improved Essays