Describe some of the traditional methods for identifying bac

Describe some of the traditional methods for identifying bacteria and their advantages.

Solution

The traditional methods involve phenotypic identification of bacteria. In which the following methods use:

Gram staining: Gram staining is a staining method i.e. coloring method. This technique belongs to staining of cell wall of bacteria. Some bacteria have thick peptidoglycan layer than other bacteria. Therefore, gram staining used this difference to distinguish between them. The thick layer can retain large molecule of staining material by adding iodine. Iodine binds crystal violet to the cell wall and when the culture washes with decolorizing material like alcohol or acetone, the thick walled cells do not lose the crystal violet. So crystal violate is used to distinguish thick walled bacteria and termed them gram positive. To identify others, gram negative, safranin like lightweight coloring compound uses. This takes up by both cells but can visible only in gram negative because the decolonization process washed out crystal violet from their cell walls.

Culture method: this technique depends upon the morphological characteristics which can observable under microscope. The different bacteria characteristics take consider when to classify a particular bacterium. For example, anaerobic and aerobic culture, source of energy dependent culture like glucose or sucrose or fructose dependent and nitrogen source dependent culture like as tryptophan or arginine.

Biochemical method: the method uses when some bacteria exhibit similar characteristics during culture method. That involves the various types of agar medium. For example, Eosin methylene blue agar uses to grow gram-negative bacteria especially coliform. EMB contain a methylene blue dye, which permeate the wall of gram-positive bacteria. On other hand, the EMB allows to grow only lactose fermenting bacteria because the compound forms by eosin and methylene blue only takes by lactose fermenters. Fecal coliform bacteria made green or dark color (black/purple or dark blue) colonies in EMB agar plates. While other coliform bacteria represent in light color such as pink or slimy appearance. Other agar mediums are use: MacConkey agar, Hektoen enteric agar and yeast extract, malt extract agar.