![]() The Gram stain, developed by Christian Gram in 1884, is the most widely used differential stain in bacteriology. The Gram Stain Shows Differences in Cell Wall Structures Capsules appear as transparent halos around dyed cells. The capsule stain determines if a bacterial species has capsules or not. The result shows the background as dark, the cells the color of the counterstain, and the capsule (if present) appearing clear. The capsule stain uses the following dyes: India ink or nigrosin (stains the background, not cells) and a counterstain. The flagella stain is used to visualize flagella (if present). The flagella stain uses the following dyes/reagents: tannic acid or potassium alum mordant, pararosaline or basic fuchsin. ![]() Endospores (if present) appear bluish-green and all other cells/cell structures appear pink. The endospore stain is used to distinguish between bacterial species that do and do not form endospores. The endospore stain uses the following: heat, malachite green, and safranin. Acid fast bacteria appear read and non-acid fast bacteria appear blue. Gram staining is an empirical method of differentiating bacterial species into two large groups (Gram-positive and Gram-negative) based on the chemical and. The acid fast stain is used to distinguish acid fast bacteria (reveals the cell wall structure of certain types of bacteria beyond Gram-positive and Gram-negative). The acid fast stain uses the following dyes: basic fuchsin and methylene blue. The Gram stain distinguishes cells by cell wall type (Gram-positive or Gram negative). The Gram stain uses the following dyes/reagents: crystal violet, Gram's iodine, ethanol, and safranin. Table 1: Summary of some common differential stains used in microbiology. Some examples of differential stains are the Gram stain, acid-fast stain, and endospore stain. Differential stains use more than one stain, and cells of different bacterial species can have different appearances based on their chemical or structural properties. ![]() Microbiologists commonly perform differential stains, as this allows them to gather additional information about the bacteria they are working with. Troubleshoot unsuccessful Gram stains and explain how errors might be fixed. ![]()
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