Gram positive cells take up the crystal violet, which is then fixed in the cell with the iodine mordant. This forms a crystal-violet iodine complex which remains in the cell even after decolorizing. It is thought that this happens because the cell walls of gram positive organisms include a thick layer of protein-sugar complexes called peptidoglycans. This layer makes up 60-90% of the gram positive cell wall. Decolorizing the cell causes this thick cell wall to dehydrate and shrink, which closes the pores in the cell wall and prevents the stain from exiting the cell. At the end of the gram staining procedure, gram positive cells will be stained a purplish-blue color.
Gram negative cells also take up crystal violet, and the iodine forms a crystal violet-iodine complex in the cells as it did in the gram positive cells. However, the cell walls of gram negative organisms do not retain this complex when decolorized. Peptidoglycans are present in the cell walls of gram negative organisms, but they only comprise 10-20% of the cell wall. Gram negative cells also have an outer layer which gram positive organisms do not have; this layer is made up of lipids, polysaccharides, and proteins. Exposing gram negative cells to the decolorizer dissolves the lipids in the cell walls, which allows the crystal violet-iodine complex to leach out of the cells. This allows the cells to subsequently be stained with safranin. At the end of the gram staining procedure, gram negative cells will be stained a reddish-pink color.
Remember:
If the Gram Stain is completed properly, gram positive should stain purple; however, if you over decolorize a gram positive organism, the organism will appear appear pink, which is a gram negative reaction. To summarize, if you over decolorize a gram positive organism it will show as a gram negative organism.
Bile salts in Eosin Methylene Blue agar inhibit the growth of Gram-positive bacteria, allowing for the selective growth of Gram-negative bacteria. This helps in the detection and differentiation of organisms based on their ability to ferment lactose and produce acid.
Post ID Special:Contributionssaid: "blue-violet.....because it is a gram-negative bacteria"Wrong...the color is correct, but S. aureus is gram-POSITIVE.
Staphylococcus bacteria typically do not grow well on Eosin Methylene Blue (EMB) agar. EMB agar is selective for gram-negative bacteria, particularly Enterobacteriaceae, and contains dyes that inhibit the growth of gram-positive bacteria like Staphylococcus.
Methylene blue is an appropriate dye because it readily binds to the negatively charged components of bacterial cells, such as nucleic acids and proteins. This binding allows for clear visualization of bacterial morphology and intracellular structures under a microscope. Additionally, methylene blue is a relatively simple and cost-effective stain to use in microbiology.
Eosin and methylene blue dyes present in EMB (Eosin Methylene Blue) agar inhibit the growth of gram-positive organisms by interfering with their ability to take up nutrients and causing damage to their cell walls. This makes the medium selective for gram-negative bacteria, allowing them to grow while inhibiting the growth of gram-positive bacteria.
If the Gram Stain is completed properly, gram positive should stain purple; however, if you over decolorize a gram positive organism, the organism will appear appear pink, which is a gram negative reaction. To summarize, if you over decolorize a gram positive organism it will show as a gram negative organism.
Bile salts in Eosin Methylene Blue agar inhibit the growth of Gram-positive bacteria, allowing for the selective growth of Gram-negative bacteria. This helps in the detection and differentiation of organisms based on their ability to ferment lactose and produce acid.
Their eggs can be from a teal with brown spots to a light blue with spots.
pale or grayish blue with spots of purple gray or blue
Dang, dude!
A greyish blue but, more grey then blue. They also have white spots and strips. Strips on the back and, a lot of spots on his head
Most gram positive bacteria do not grow on MacConkey agar or Eosin Methylene Blue (EMB) agar, as these are selective media designed to inhibit the growth of gram positive organisms. So, typically, you would not expect a gram positive bacteria to grow on these media.
Gram-negative bacteria Gram-negative bacteria have an outer membrane. However, they have a thinner peptidoglycan cell wall. This means they do not hold the blue dye used in Gram testing and do not appear blue. Instead, they appear red or pink in color.
Post ID Special:Contributionssaid: "blue-violet.....because it is a gram-negative bacteria"Wrong...the color is correct, but S. aureus is gram-POSITIVE.
The presence of thick cell wall. Gram positives have a thick cell wall and remain blue. Gram negatives have a thin cell wall where the blue stain washes out and then will stain pink with the counter stain.
7.5