Question

What is the difference between a negative stain bacteria and a capsule stain bacteria

Answer 1

Negative stain bacteria:

Negative stain is mainly used for various studies such as morphological shape, the size as well as the arrangement of the bacteria cells which are difficult to stain. They are also helped in staining the cells which are too delicate to be heat fixed. Negative staining is also used for the preparation of biological samples for the electron microscopy. Helps in viewing bacteria, flagella of bacteria, viruses and the biological membrane structures and the proteins or the protein aggregates which all are basically have a low electron scattering power. Example: Spirilla.

In this method, the specimen is left untouched whereas the background gets stained and thus is visible. Thus negative staining requires an acidic dye (Such as Nigrosin or India Ink) These acidic stain will gives upon the hydrogen ion or the proton and the chromophore of dye would become negatively charged. Since the cell surface of most of the bacteria cells are negatively charged, these would repel the stain. This would result in showing off of the bacterial cell wall as clear spots against a dark background.

Capsule stain bacteria:

Capsule staining is mainly done to distinguish the capsular material from the bacterial cell wall. Capsule is an outer layer, gelatinous form, which is secreted by the bacterial cell which is surrounded and adhered to the bacterial cell wall. Most of the capsules are mainly composed of polysaccharides and some of polypeptides. The capsule of different bacteria differs from the slime layer, as most of the bacteria produce in that it is a thick,detectable and discrete layer outside the cell wall. The capsule stain of bacteria employs an acidic stain as well as a basic stain for detection.