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Unformatted text preview: Microbiology Made Ludicrously Simpler (Jarrods key for MOD and USMLE) Gram Stain separates bact into two major groups Procedure = crystal violet stain wash with water flood with iodine wash with water decolorize with alcohol counter stain with safranin o Gram-positive holds crystal violet and appear blue o Gram- negative crystal violet washed away by alcohol. Cells absorb safranin ( red) Bacterial cell membrane/cell wall Peptidoglycan layer = cell wall - layer outside plasma membrane. Present in G+ and G- o Transpeptidase (penicillin binding protein) cross linkages in peptidoglycan layer Target of penicillin o G+ - cell wall is thick with extensive cross-linking Contains teichoic acid = antigenic determinant helpful in ID of many G+ species NO ENDOTOXIN (exception = Listeria monocytogenes = TQ) o G- - cell wall is thin with simple cross-linking. NO teichoic acid G- cell wall 3 layers. From inside to out, they are: o Plasma membrane Periplasmic space b/w PM and peptidoglycan layer o Thin peptidoglycan layer murein lipoprotein links this layer to the outer PM o Outer cell membrane contains LPS. Protects cell wall from some abx (e.g. pcn) LPS three components O-antigen outer component. Antigenic determinant. Core polysaccharide Lipid A = Endotoxin . All G- possess. o Lysing of bact by immune system and/or abx release of lipid A fever, diarrhea, shock (septic shock) Bacterial Morphology Cocci spherical Bacilli rods (short rods are called coccobacilli) Spiral forms comma, S or spiral shaped Pleomorphic no distinct shape G+ bacteria assoc with human dz (only 6) Streptococcus strips of cocci Staphylococcus clusters of cocci Spore formers o Bacillus o Clostridium Corynebacterium Listeria G- Diplococcus ( Neisseria ) is the only G- coccus All other gram negative organisms are rods or pleomorphs Others Mycobacteria acid-fast stain (bugs that cause tuberculosis and leprosy) Spirochetes gram negative, but too small to be seen with light microscopy. Can be seen via dark field microscopy Mycoplasma no cell wall neither G+ nor G- Bacterial ribosomes 70S. Sub-units 30S (inhibited by s) and 50S (inhibited by macrolides) Oxygen and Carbon Source Macrophages produce oxyradicals to destroy bacteria How do bacteria deal with oxyradicals (oxidative stress)?...
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This note was uploaded on 06/17/2008 for the course MOD 2 taught by Professor Cunningham during the Spring '08 term at University of North Texas Health Science Center.
- Spring '08
- The Hours