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## Microorganisms ### Biology Grade 12 #### Self-Questioning * What are other ways of classifying bacteria? * Define or describe the following: outer membrane, periplasmic space, envelope, teichoic acid, adhesion site, lipopolysaccharide, and porin protein. * Describe in detail the structure and...

## Microorganisms ### Biology Grade 12 #### Self-Questioning * What are other ways of classifying bacteria? * Define or describe the following: outer membrane, periplasmic space, envelope, teichoic acid, adhesion site, lipopolysaccharide, and porin protein. * Describe in detail the structure and composition of peptidoglycan of, gram-positive and gram-negative cell walls. Include labeled diagrams in your answer. * Explain the role of a cell wall in protecting against lysis and illustrate how this role may Besides their shape bacteria can be classified based on their cell wall composition. One of these ways is whether they are retaining dyes during Gram's stain (Figure 2.6). In this case, bacteria can be categorized into two: * **Gram-Positive:** Gram-positive bacteria have a distinctive purple appearance when observed under a light microscope following Gram staining. This is due to retention of the purple crystal violet stain in the thick peptidoglycan layer of the cell wall. Examples of Gram-positive bacteria include all *staphylococci*, all *streptococci* and some *listeria* species. * **Gram-Negative:** Gram-negative bacteria lose the crystal violet stain (and take the color of the red counterstain) in Gram’s method of staining. This is characteristic of bacteria that have a cell wall composed of a thin layer of a particular substance (called peptidoglycan). #### Self-Questioning How does the gram stain procedure differentiate bacteria? ## Unit 2: Microorganisms ### Biology Grade 12 - Gram Positive - Gram Negative