BIOS 242 Week 3 Assignment; Lab 5 of 14 Onsite; Differential Staining

$10.00

Contributor

Matthew Lillard

Category

Biosciences

Course

BIOS 242 Fundamentals Of Microbiology With Lab

Institute

Chamberlain

Pages

17

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Lab 5: Differential Staining Learning Objectives: Explain the principle of differential staining Apply differential staining to identify bacteria Differential stain uses two or more stains to specifically stain certain structures or cellular components which cannot be easily observed using simple stains. Differential staining principles are based upon the specific chemical nature and composition of cellular components and therefore, different structures are observed using different stains and staining procedures. Differential staining often becomes the basis of identification of the bacteria in clinical labs. In this lab, we will learn about four separate staining procedures. Gram Staining Endospore Staining Acid-fast Staining Capsule Staining (Special Staining) Exercise 1: Gram Staining Gram staining is used to identify cells based on the differences of the cell wall. While some bacteria may contain a thick layer of peptidoglycan that forms a thick rigid cell wall (Gram positive), other bacteria have a very thin layer of peptidoglycan forming a thin cell wall sandwiched between two cell membranes (Gram Bacteria with thin cell wall Bacteria with thick cell wall Primary Stain: Crystal Violet Mordant: Iodine negative). The outer membrane is rich in lipopolysaccharides (LPS). Gram staining takes advantage of these differences in the cell wall of bacteria. Using two different stains that offer a lot of contrast, bacteria Decolorizing agent: Acetone/Alcohol BIOS242 Lab 5 Name: containing a thick cell wall are stained purple. They are called Gram-positive cells. Bacteria containing a thin cell wall are stained pink and are called Gram- negative cells. In Gram staining, bacteria are first treated with a primary stain, crystal violet. Upon treatment with crystal violet, all cells are stained purple irrespective of presence of thick or thin cell wall. Stained bacteria are then treated with a mordant, iodine. Iodine helps crystalize crystal vi

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