Lecture 2 - Pathogenesis

Lecture 2 - Pathogenesis - EVO MICROBIAL PATHOGENESIS Edwin...

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Unformatted text preview: EVO MICROBIAL PATHOGENESIS Edwin Oaks, Ph.D. George Mason University Fall 2008 EVO BACTERIA OVERVIEW EVO Review of Gram-Positive Bacteria Gram-positive bacteria have a single plasma membrane or inner membrane and a thick cell wall consisting of multiple layers of peptidoglycan. The cell wall functions as a surface organelle for the display of carbohydrates and proteins Gram-positive bacteria can form spores - highly resistant to environmental extremes Bacillus anthracis Clostridium tetani EVO Gram-positive Cell Wall Peptidoglycan Wall teichoic acid Cell wall Plasma membrane Lipoteichoic acid Protein EVO Review of Gram-Negative Bacteria Gram-negative bacteria possess a double membrane. The inner (cytoplasmic) membrane can perform active transport, has respiratory chain components, and various proton pumps. The periplasm contains various degradation enzymes, and signaling molecules. The outer membrane functions as a surface organelle for the display of carbohydrates and proteins and contains porins, transporters, lipopolysaccharides and a thin peptidoglycan layer. Murein lipoprotein tethers the outer membrane to the peptidoglycan layer. Type III secretion system (TTSS) EVO Gram-negative Cell Wall Cell wall Plasma membrane LPS Lipid A O polysaccharide Peptidoglycan Phospholipid Lipoprotein Enzymes Outer membrane Periplasmic space Porin protein EVO Structure of LPS Hep Kdo n GlcN Hep Hep Kdo P-P-P-P-O-specific Chain Core Lipid A Polysaccharide Glycophospholipid Outer Core Inner Core NH 3 + Abbreviations GlcN: glucocosamine Hep: L-glycero-D-manno-heptose Kdo: 2-keto-3-deoxyoctulosonic acid P: phosphate zig-zag lines:fatty acids Adapted from Caroff et al, 2002 EVO Comparative Characteristics Characteristic Gram-Positive Gram-Negative Gram reaction Retain crystal violet Can be decolorized Peptidoglycan layer Thick Thin Teichoic acids Present in many Absent Periplasmic space Absent Present Outer membrane Absent Present LPS content none High Lipid/lipoprotein content Low High Flagellar structure 2 rings in basal body 4 rings in basal body Toxins produced Primarily exotoxins Exo- and endotoxins Type III Secretion System Absent Present Adapted from Tortora et al. 1997 EVO Bacterial Cell Structure EVO Bacterial Appendages Pili Hollow, hairlike structures made of protein, allow bacteria to attach to other cells including mammalian cells A specialized pilus, the sex pilus, allows the transfer of DNA from one bacterial cell to another. Pili (sing., pilus) are also called fimbriae (sing., fimbria). Type III Secretion Apparatus Surface apparatus made of protein subunits that injects host-specific virulence factors into eukaryotic cells through a hollow needle-like structure Spans inner and outer membrane of gram negative bacteria EVO Bacterial Appendages, cont....
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This note was uploaded on 04/29/2009 for the course BIOL 420 taught by Professor Edwardsoaks during the Fall '08 term at George Mason.

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Lecture 2 - Pathogenesis - EVO MICROBIAL PATHOGENESIS Edwin...

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