Though Gram staining is a great method for observing bacteri

Though Gram staining is a great method for observing bacteria in the microscope, there are reasons why negative staining (with nigrosin) is better than Gram staining. Briefly describe three of these reasons. (Note: your three reasons must be distinctly different from each other, and your answer must be fewer than 75 words).

Solution

Negative staining-the main purpose is to study the morphological shape, size and arrangement of the bacterial cells that is difficult to stain.

It can also be used to stain cells that are too delicate to be heat fixed.

It is alos used to prepare biological samples for electron microscopy. Its used to view viruses, bacterial flagella, bacteria, biological membrane structure, proteins and protein aggregates, which all have a low electron scattering power. Its also used for the identification of aqueous lipid aggregates like lamellar liposomes, inverted spherical micelles, and inverted hexagonal HII cylindrical (H) phases by negative staining electron transmission.

Nigrosin is an Acidic Stain- which means that it easily gives up a Hydrogen ion (proton), and the chromophore of the dye becomes negatively charged. Sine the surface of most bacterial cells is negativly charged, the cell surface repels the stain, the glass of the slide will stain but the cell will not.