The simple staining procedure makes to visualize bacteria clearly, but it does not distinguish between organisms of similar morphology. The Gram staining method is named after the Danish bacteriologist (1882) Hans Christian Gram, is one of the most important staining techniques in microbiology. It is almost always the first test performed for the identification of bacteria. The primary stain of the Gram's method is crystal violet. Crystal violet is sometimes substituted with methylene blue, which is equally effective. The microorganisms that retain the crystal violet-iodine complex appear purple brown under microscopic examination. These microorganisms that are stained by the Gram's method are commonly classified as Gram-positive or Gram non-negative. Others that are not stained by crystal violet are referred to as Gram negative, and appear red. In this method the fixed bacterial smear is subjected to the following staining reagents in the order of sequence listed below Primary stain Crystal violet is used first and stains all cell purple = Mordant = Grams iodine serves as a mordant, a substance that increases the cell affinity for a stain. It does this by binding to the primary stain thus forming an insoluble complex. The resultant crystal violet iodine complex serves to identify the color of the stain. At this point all cells will appear purple black. = Decolorizing agent = Gram staining is based on the ability of bacteria cell wall to retaining the crystal violet dye during solvent treatment. The cell walls for Gram-positive microorganisms have a higher peptidoglycan and lower lipid content than gram-negative bacteria In Gram-negative cells, subsequent treatment with a decolorizer, (95% ethyl alcohol) dissolves the lipid layer from the gram-negative cells. The removal of the lipid layer enhances the leaching of the primary stain from the cells into the surrounding solvent. In contrast, the solvent dehydrates the thicker Gram-positive cell walls, closing the pores as the cell wall shrinks during dehydration. As a result, the diffusion of the violet-iodine complex is blocked, and the bacteria remain stained. Counter stain A counterstain of basic fuchsin or saffranin is applied to the smear to give decolorized gram-negative bacteria a pink color. Since only gram-negative cells undergo decolorization they may now absorb the counter stain. Gram-positive cell retain the purple color of the primary stain. Basic fuchsin stains many Gram-negative bacteria more intensely than does safranin, making them easier to see. Some bacteria which are poorly stained by safranin, such as Haemophilus spp., Legionella spp., and some anaerobic bacteria, are readily stained by basic fuchsin, but not safranin. The polychromatic nature of the gram stain enables determination of the size and shape of both Gram-negative and Gram-positive bacteria. If desired, the slides can be permanently mounted and preserved for record keeping.
Gram positive bacteria appear purple or blue when stained with the Gram stain, while gram negative bacteria appear pink or red. This color difference is due to the thickness of the cell wall and the presence of an outer membrane in gram negative bacteria.
After the addition of mordant in the Gram stain, gram-negative bacteria will appear red or pink under the microscope. This is because the mordant helps to fix the crystal violet stain to the cell wall of gram-positive bacteria, making it harder for the decolorizer to remove it from the thicker peptidoglycan layer of gram-positive bacteria.
Yogurt contains mostly lactic acid bacteria, which are Gram-positive bacteria. This means they will stain purple under a Gram stain.
The color of a gram-negative stain is pink or red. This staining technique is used to differentiate bacteria based on their cell wall composition, with gram-negative bacteria retaining the pink/red color after staining.
When performing the Gram stain, acetone is used as a wash step between the iodine and safranin. By not washing, all stains will remain crystal violet purple, and none will appear safranin red/pink.
Gram-positive bacteria retain the crystal violet stain and appear purple when stained with Gram's stain, because the thick peptidoglycan layer in their cell wall traps the dye. On the other hand, Gram-negative bacteria do not retain the crystal violet stain and appear red or pink after the addition of a counterstain like safranin, due to their thin peptidoglycan layer which is unable to retain the dye.
The Gram stain determines the cell wall composition of bacteria. It categorizes bacteria into two groups based on their ability to retain or release a purple dye: Gram-positive bacteria retain the dye and appear purple, while Gram-negative bacteria do not retain the dye and appear pink. This staining technique is commonly used in microbiology to help identify and classify bacteria.
Some bacteria will appear purple, whereas other bacteria will appear red.
Gram positive bacteria appear purple or blue when stained with the Gram stain, while gram negative bacteria appear pink or red. This color difference is due to the thickness of the cell wall and the presence of an outer membrane in gram negative bacteria.
If iodine is not applied, both the gram-positive and gram-negative stains will appear to be gram-negative. The iodine acts as a mordant that helps to fix the crystal violet stain in the gram-positive bacteria, making them appear purple. Without iodine, the crystal violet stain can be easily washed out of both gram-positive and gram-negative bacteria, resulting in a pink or red color.
After the addition of mordant in the Gram stain, gram-negative bacteria will appear red or pink under the microscope. This is because the mordant helps to fix the crystal violet stain to the cell wall of gram-positive bacteria, making it harder for the decolorizer to remove it from the thicker peptidoglycan layer of gram-positive bacteria.
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The purple stained bacteria are called gram positive bacteria and retain the stain after washing by having a thick cell wall one one layer of a heavily crossed linked material called peptidoglycan. ( Google that ) The red stained bacteria are gram negative because they posses two thinner layers of peptidogylcan cell wall that that do not hold the gram stain and it is mostly washed away in rinsing the bacterial samples.
Yogurt contains mostly lactic acid bacteria, which are Gram-positive bacteria. This means they will stain purple under a Gram stain.
Bacteria are gram positive or gram negative. Serratia happens to be a gram negative bacteria. They appear pink on a gram stain. Gram positive bacteria stain to a purple color on a gram stain. We can classify and ID bacteria using their gram stain and shape. Some antibiotics only work on gram negative bacteria and some only work on gram positive bacteria. It helps a doctor know which antibiotic to use.
The color of a gram-negative stain is pink or red. This staining technique is used to differentiate bacteria based on their cell wall composition, with gram-negative bacteria retaining the pink/red color after staining.
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