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Why do Gram positive bacteria retain crystal violet stain and remain purpule?
Wiki User
∙ 13y ago
This is a fairly difficult question to answer. Most readings will only tell you that bile salts and crystal violet inhibit gram-positive growth but do not say why. I found some articles that probably would tell us why, but you must pay to subscribe to them. I do know why crystal violet inhibits gram-positive growth though. Crystal violet binds to the peptidoglycan layer of cell membrane in gram-positive bacteria (just like it does in the Gram stain). Gram-negative bacteria have an outer membrane that prevents the crystal violet from attaching to their peptidoglycan layer. Once crystal violet attaches to the peptidoglycan, enzymes called autolysins are unable to cut the polysaccharide linkages between the NAG and NAM residues. The cutting and reforming of the peptidoglycan layer is necessary for cell growth, thus killing the cell. I believe that bile salts work a very similar way just like how penicillin and lysozymes do.
Wiki User
∙ 14y ago
Wiki User
∙ 9y agoSelective contains bile salts and crystal violet that inhibit the grow of Gram plus organisms selects for gram organisms. Differential- contains lactose and pH indicator (neutral red)- differentiates between lactose fermenters (reddish colonies) and non-fermenters (clear to colorless colonies).
Wiki User
∙ 13y agoMost gram-positive bacterial cells have a very thick, rigid peptidoglycan cell wall. The abundance and thickenss (25mm) of this material may be one reason why they retain the crystal violet in the Gram stain.
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∙ 13y agoMost gram-positive bacterial cells have a very thick, rigid peptigdoglycan cell wall. The abundance and thickenss (25mm) of this material may be one reason why they retain the crystal violet in the Gram stain.
Wiki User
∙ 11y agoThe mode of action put forward by Steam & Stearn (1928) that the action of crystal violet is due to the formation of an unionized complex of bacteria with dye, is supported. Gram-negative organisms, such as E. coli, have high isoelectric points and contain less acidic components than Gram-positive bacteria which usually have lower isoelectric points, so the former combine with crystal violet less readily and are more resistant to the dye. In extension of this theory, the negative charge on bacteria is increased as the pH of the medium is increased, and the organisms become more sensitive to dye.
Wiki User
∙ 11y agobecause it cannot be trapped by peptidoglycan layer
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∙ 12y agoAsk Kenneth yu
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What happens if not enough alcohol is applied to a gram stain?
Both bacteria types would be stained by the safranin. When the iodine is added, safranin would be "set" in the positive. The decolorizer would wash out the safranin and then application of the crystal violet would stain the negative.
Function of Gram's iodine?
Iodine is used as a mordant in the gram staining procedure to make large crystals when it is used with crystal violet dye. In gram positive cell walls those crystals get stuck and wont get washed off with the alcohol. In gram negative cell walls the crystals are washed out.
Does cooked food remain free from pathogenic bacteria?
once you have cooked food will in remain free from pathogenic bacteria
What do bacteria form in order to remain dormant for years?
An endospore
Bacteria that remain inactive until enviormental conditions are favorable?
These can produce endospores.
What is the function of safranin in the Gram staining process?
Crystal violet is used first to stain all bacteria purple. However, when you immerse the bacteria then in alcohol, alcohol affects the permeability of the peptidoglycan layer to crystal violet, blocking its exit from gram-positive cells. This way, gram-positive cells remain purple while gram-negative cells are colourless. Safranin red is then used as a counterstain to make the two types of bacteria more differentiable.
What happens if not enough alcohol is applied to a gram stain?
Both bacteria types would be stained by the safranin. When the iodine is added, safranin would be "set" in the positive. The decolorizer would wash out the safranin and then application of the crystal violet would stain the negative.
What is the stainning method called that can distinguish between two different types of eurobacteria?
I believe what you're looking for is the stain that can differentiate between Gram-negative and Gram-positive bacteria: two types of eubacteria. So the staining method is called the Gram method. Crystal violet will remain trapped in Gram-positive bacteria due to their thicker cell walls, causing them to stain purple. Crystal violet can be washed out of Gram-negative cell walls after alcohol treatment to remove their outer lipid membrane, and the cells can be counterstained with a red, positively charged stain. In the end, Gram-positive bacteria will look purple, and Gram-negative bacteria will look red. See Wikipedia for more details.
Function of Gram's iodine?
Iodine is used as a mordant in the gram staining procedure to make large crystals when it is used with crystal violet dye. In gram positive cell walls those crystals get stuck and wont get washed off with the alcohol. In gram negative cell walls the crystals are washed out.
What is the function of iodine solution in the gram stain?
It allows the primary stain crystal violet to remain in the cell instead of being washed out. Due to the larger size of the crystal violet molecule, when the ethanol is applied (the decolorizer) the stain will not be washed out of the Gram (+) positive cells.
Is staphylococcus aureus positive for gelatin hydrolysis?
Bacillus cereus is positive for gelatin hydrolysis. This bacteria is capable of hydrolyzing gelatin(a protein), thus, a nutrient gelatin medium inoculated with this bacteria will remain liquid when placed in an ice bath (don't agitate).the bacteria had proteases that is responsible for the hydrolysis of the gelatin..
Does cooked food remain free from pathogenic bacteria?
once you have cooked food will in remain free from pathogenic bacteria
When dissolved in water what will not happen to a salt crystal?
The chemical composition remain unchanged.
What do bacteria form in order to remain dormant for years?
An endospore
Bacteria that remain inactive until environmental conditions are favorable?
Endospores.
Why would gram negative bacteria appear purple after gram stain?
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.
If a function is positive at a test number it will remain positive until it reaches zero or a vertical asymptote?
true
