Gram negative outer membrane this is outside of the

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• Gram Negative - Outer Membrane This is outside of the Cell Wall - Thin Peptidoglycan Layer Possibly a single, interconnected Molecule of Peptidoglycan. - Periplasm The Area between the Outer Membrane and the Cell Membrane. Gram Positive Cell Walls • Thick Cell Wall composed mostly of Peptidoglycan - But may also contain Teichoic Acid (G= wall) • Teichoic Acids are only found in Gram Positive Bacteria • Tetrapeptide Side Chains are linked by Peptide Interbridges composed of several Amino Acids NAG - NAM - NAG | AA | AA | AA AA | | AA- aa - aa - aa - aa - aa -AA | Peptide Interbridge AA | AA | NAG - NAM - NAG Any of the four Amino Acids in the Tetrapeptide Side Chains can be present in the Peptide Interbridges. Other Amino Acids, particularly Glycine, Theronine, Serine, and Aspartic Acid, can also be present and their Presence is Species Specific.
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Structure of Bacteria Page 4 Gram Negative Cell Walls • Thin Cell Wall composed entirely of Peptidoglycan - Usually only 1 or 2 Layers Thick • Tetrapeptide Side Chains are directly linked NAG - NAM - NAG | AA | AA | AA AA | | AA- - -AA | Direct Link AA | AA | NAG - NAM - NAG • Outer Membrane - The Outer Membrane is much less permeable than the Cell Membrane • Porin Proteins join to form Transmembrane Channels - Porins give Gram Negative Bacteria Control over the Entry of Toxic Substances and Antibiotics - The Outer Membrane contains Lipopolysaccharides (LPS) • LPS are found only in the Outer Membrane of Gram Negative Bacteria The Immune System ʼ s almost hysterical Response to LPS gives rise to many Symptoms of Diseases caused by Gram Negative Bacteria • Periplasm (G = form around [perimeter]) - The Area between the Outer Membrane and Cell Membrane - Gel-like Matrix containing Hydrolytic Enzymes and Binding Proteins • Initial Degradation of Nutrients (and Antibiotics) • Transport of Stuff The Periplasm is sorta like the screened-in Porch of a Summer Home. It isn ʼ t Inside; it isn ʼ t Outside; and lots of interesting Stuff usually take place there.
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Structure of Bacteria Page 5 Capsule (L = little box) • Diffuse Layer outside of the Cell Wall - Helps resist Phagocytosis - Excludes Bacteriophage (G= bacteria eaters [Bacterial Viruses]) - Protects from Desiccation • Usually composed of Polysaccharides - Can be Homopolymers (G= same) or Heteropolymers (G= different) • Some Capsules are composed of Polypeptides - The Amino Acids can be D Stereoisomers • D Stereoisomers are never found in Proteins on this Planet Biofilms • Matrix outside of the Cell Wall - Biofilms are Populations or Communities of Microbes attached to a Surface and contained within an extracellular Polysaccharide Matrix • Matrix Formation only occurs when a minimum Number (Quorum) of Bacteria have colonized a Surface Biofilm Formation may be the Default Mode of Bacterial Growth in Nature, be that Growth on a Rock or in your Urethra. Pure Culture and Batch Culture are increasingly seen as incredibly Artificial Bacterial Growth Conditions.
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