When a stain, such as an acid dye, cannot penetrate the outer layers of a microbe, the cell will appear transparent on a colored background. This stain is called a negative or background stain. It is performed by mixing the dye with a suspension of bacteria on a slide and spreading the mixture into a thin layer for viewing. The capsule is a structure surrounding the cell wall that certain bacteria can produce. The ability to form a capsule is genetically and environmentally controlled. Only those microbes with the genes for capsule production have the potential to manufacture this polysaccharide (or polypeptide) surface layer. Special nutrients or other growth factors often are necessary for the genes to be expressed. The role of the capsule is primarily for protection of the bacteria. For example, the capsule affords a seal against dehydration. Many capsules repel white blood cells and thus allow pathogenic invading bacteria to elude one of the primary host defenses. Capsules are not readily stained and therefore are visualized by negative stain techniques. The organisms are prepared as a smear in the presence of an acid dye and allowed to air dry because heat will cause the capsule to shrink. Our procedure will combine a negative stain (which colors the background) and a simple stain to color the bacterial cell. The capsule appears as a colorless layer between the bacterium and the background.
its red & yellow.
capsule
capsule does not gets stained it appears to be colourless when stained using manewals staining procedure
For the capsule stain Congo red or a Nigrosin solution can be used. Next, Maneval's stain is used.
yes as it have capsule it give positive test for capsule staining when stain with malachite green The problem with the above answer is that a capsule stain is NOT done with malachite green.
Capsule Stain
capsule
capsule does not gets stained it appears to be colourless when stained using manewals staining procedure
I dont have any answer, But i will post it when i will know . No change in color or reaction on Indole Test - Negative result on Indole Test.
For the capsule stain Congo red or a Nigrosin solution can be used. Next, Maneval's stain is used.
to stain the outside and the inside of the cell.. so the capsule appears transparent
yes as it have capsule it give positive test for capsule staining when stain with malachite green The problem with the above answer is that a capsule stain is NOT done with malachite green.
Capsule Stain
capsule
Demonstrating the presence of a capsule is a means of diagnosis and determining the organisms virulence.
The copper sulfate is used as a decolorizing agent rather than water. The copper sulfate washes the purple primary stain out of the capsular material without removing the stain bound to the cell wall. At the same time, the decolorized capsule absorbs the copper sulfate, and the capsule will now appear white in contrast to the deep purple of the cell.
From what i read in my book: Because the capsule is nonionic, unlike the bacterial cell, the primary stain adheres to the capsule without binding to it. Since the capsule is water- soulube, copper sulfate, rather than water, is used to wash the purple primary stain out of the capsular material without removing the stain that is bound to the cell wall.
capsule