Microbiology Lecture 3.docx - Teichoic acid Glycopolymers that determine cell shape and regulate cell division Can be found in the cytoplasmic membrane

Microbiology Lecture 3.docx - Teichoic acid Glycopolymers...

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Teichoic acid Glycopolymers that determine cell shape and regulate cell division Can be found in the cytoplasmic membrane, cell wall, and capsule of Gram-positive bacteria (Gram-negative do not have this) Responsible for the negative charges of the bacterial cell surface Periplasm Space between the inner (cytoplasmic) and outer membranes in Gram-negative bacteria In Gram-positive bacteria, periplasm is found between the inner membrane and the thick peptidoglycan layer Metabolically dynamic area that contains proteins called enzymes and thin peptidoglycan layer o Enzymes break down cell wall and molecules Gram-Stain Procedure Differentiates gram-positive bacteria from gram-negative bacteria and vice versa Gram-positive bacteria (with about 40 layers of peptidoglycan) stain purple o Process: purple dye goes into the negative bacterial cell, interacts with gram iodine, forms a complex, purple dye gets trapped inside the cell Gram-negative bacteria (with about 8 layers of peptidoglycan) o Process: purple iodine complex is washed out because the thin peptidoglycan layer does not allow the purple dye to stay in, the negative cell gets no color (negative stain repels negative cell) while the background is stained, so people counterstain using red dye called sacranin Gram-negative bacteria Have an outer membrane while the Gram-positive do not Certain antibiotics do not work because they cannot get through the outer membrane Contain Lipopolysaccharide (LPS) that sticks out of the outer membrane of the cell wall o LPS is only found in a gram-negative microorganism o A very repetitive structure (carbohydrates hanging off the chains of glucosamine- pyrophosphate) Lipid A (part of LPS) causes the toxicity of the gram-negative bacteria o Causes blood vessels to dilate Causes septic shock
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o Endotoxin molecule Types of bacterial cells Acid-fast bacteria o Name refers to the stains (they stain red) that are used to identify these organisms o
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