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Gram Stain and Bacterial Cell Wall Structure
Once it became established that bacteria can cause illness, the scientist studying these minute microbes needed to find a way to view and identify them. The Gram stain was invented in the 1800's by Christian Gram and is still the initial test used when establishing the identity of bacteria.
Gram is a differential stain that uses a series of dyes to essentially divide the bacterial world in two;Gram-positive bacteria and Gram-negative bacteria. The distinction between these two bacterial types is based on differences in the cell wall structure of these microbes.
Articles on Bacterial Cell Wall and Gram Stain
Bacteria Gram Stain Reaction - Test for Gram-positive and Gram-negative Bacterial Identification: Gram staining involves the application of a series of dyes that, based on differences in bacterial cell wall structure, leaves some bacteria purple (Gram +) and others pink (Gram -). Here's how the Gram stain works.
Gram Negative ( Gram- ) Bacteria - What Makes Some Bacterial Cells Stain Gram-negative? Most bacteria have one of these two types of cell walls. Gram-positive bacteria have a cell wall made mainly of multiple layers of a strong molecule called peptidoglycan. Gram-negative bacteria have a more complex cell wall, with a small amount of peptidoglycan covered by a toxic outer LPS membrane. The differential Gram stain uses two dyes to distinguish between bacteria based on these two types of cell wall structure.
Gram+ Bacterial Stain - Peptidoglycan Cell Wall & Identification of Gram-positive Bacteria: Gram+ bacteria stain purple due to the chemistry and structure of their peptidoglycan cell wall. Here's how Gram staining works to identify Gram-positive organisms.
Gram- Bacterial Stain - Cell Wall Structure & Identification of Gram-negative Bacteria: Gram- bacteria stain pink due to the location of cell wall peptidoglycan and an external LPS membrane. Here's how Gram staining identifies Gram negative organisms.
Differential Staining of Bacteria Using Known Controls: Differential staining of bacteria employs a series of dyes to distinguish different types of bacteria based on some chemical or structural attribute of the cell. Here is an explanation of three differential bacterial staining protocols: Gram stain, Acid-fast stain and Endospore stain.
Tests for Identification of Bacteria - Differential Staining, Specialized Media and API-20E: Gram, Acid-fast and Endospore stains; MacConkey's, Mannitol Salt, and Blood Agar media as well as the API-20 test strip all provide information to help identify microbes.
- SPO Virtual Microbiology Classroom
Online information used in an actual college-level microbiology course.
- Online Textbook of Bacteriology
Todar's Online Textbook of Bacteriology has chapters on general bacteriology and pathogenic bacteria, including Staphylococcus, Streptococcus, Pseudomonas, E. coli, and agents of Anthrax, Cholera, Tuberculosis, Lyme Disease and other bacterial diseas
- Microbiology 101
Main microbiology page on the science education website Science Prof Online.
- Gram Stain Demonstration
The Microbiology Video Library with demonstration and explanation of Gram staining procedure.
- ilovebacteria - Fun science for kids!
Fun science website aimed at young people interested in science. Read science articles, try DIY science experiments, find out strange science facts, learn about microbes and more.
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