Week 1 & 2 Micro Lectures

Week 1 & 2 Micro Lectures - Lecture 1: Introduction...

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Lecture 1: Introduction to Microbiology and Bacteria Gram Stain: Provides key ID of bacteria shape and color Gram + : purple because of thick peptidoglycan prevents decoloration o Thick PG layer is barrier to lipid solvents; no not decolorize Gram - : red with safranin o Thin PG easily breached and decolorized Peptidoglycan : Rigid cell wall of bacteria Very polar; blocks entry of hydrophobic compounds Provides rigid structure to protect cytoplasm 2 sugars: (crosslinked) o N-acetylglucosamine acid o N-acetylmuramic acid Beta- 1-4 linkage of sugars broken by lysozyme in tears o Tears prevent bacteria replication in the eye Cross linked by transpeptidases o Target of Beta-lactam antibiotics Penicillin and cephalosporins Gram Positive Bacteria: Not in distinct layers Cell wall specific polysaccharides: o Key for ID in lab (antibodies react) Teichoic acid: polymers of ribitol or glycerol linked to PG or membrane o Allows for adhesion to cell surfaces and fibronectin Lipoteichoic Acid Spores: Dormant form of organism o Environmentally resistant o Coat: cross linked keratin like protein o Cortex: 2 layers of PG o Core: enzymes, chromosomes, etc to resume growth Spores: Produced by 2 medically important bacteria: Bacillus and Clostridium Resistant to heat/disinfectants Can survive in soil for years o C. tetani : spores cause tetanus o C . botulinum : in black heroin cause wound botulism Antibiotics ineffective because spores are metabolically inactive Eukaryotes vs. Prokaryotes Property Eukaryote Prokaryote Nuclear Membrane Yes No Organelles Bound Unbound Digestive Vacuoles Yes No Chromosomes Multiple Single Membrane Sterols Yes No PG in membrane No Yes Ribosomes 80s 70s Bacteria ID characteristics: Pili : small hairlike filaments made of pilin o Important for attachment in Neisseria gonorrhoeae o Specialized pili: sex pili for bacterial conjugation Capsule : acidic polysaccharides forming condensed outer layer o Blocks phagocytosis o Antibodies against capsule can be used to ID organism o Antigens in vaccines protect against capsules Ex) Pneumococcus and Haemophius vaccines o K. Pneumoniae: Larger capsule with high glucose in diabetics Increased risk of UTIs Glycocalyx : Slime layer outside of bacteria o Important in S. mutans in plaque Acid Fast Gram stain: Cell envelope unique with mycolic acids, lipids and waxes with PG Lipids resistant to decoloration with acid EtOH o Takes up gram stain poorly Gram Negative: Layers cell wall; Lipoproteins stabilized by binding PG Porins : water filled channels that allow hydrophilic nutrient movement o Nutrients bind proteins Outer membrane proteins (enable invasion) Examples- o Yersinia invasins (plague) o Gonococcal Opa proteins to avoid immune detection LPS: lipopolysaccharide o O side chain: Osmotic barrier Used to ID pathogens like Shigella and Salmonella Stimulate antibodies o Lipid A: buried in membrane
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This note was uploaded on 09/14/2011 for the course PHARM mb taught by Professor Staff during the Spring '11 term at UCSD.

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Week 1 & 2 Micro Lectures - Lecture 1: Introduction...

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