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Hemolytic patterns
- alpha: partial hemolysis, "greening" due to biliverdin
- beta: complete hemolysis, clearing
- gamma: non-hemolytic
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types of serological typing
- Lipopolysaccharide side chain ("O" antigen)
- Capsular antigen ("K" antigen)
- flagellar antigen ("H" antigen)
- other cell surface proteins (like M protein of streptococci)
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gram staining
all cells stain purple, decolorizer (alcohol or acetone) removes LPS but not peptidoglycan, so safranin colors gram-, but gram+ remains crystal violet
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acid fast stain
decolorizer (acid alcohol) takes away non-acid fast so acid-fast are red/carbolfuchsin, non are methylene blue
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peptidoglycan
thick cell wall of gram + bacteria that traps pigment (gram - has thin layer). Sugar backbone with interlocking peptides. Lysozymes break sugar backbone to make wall fall apart
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gram negative cell wall
- thin layer of peptidoglycan in periplasmic space, outer membrane is phospholipids paired with lipopolysaccharides.
- lysozymes can't cross this lipid bilayer while it's intact
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acid fast cell envelope
- mycobacterium (gram+)
- lipids on outside, mycotic acid, peptidoglycan on the bottom. Waxy cell wall, heat drives stain in.
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mollicutes and anaplasmataceae
bacteria with no cell wall. Take cholesterol from host to use. No peptidoglycan so stain gram-, but don't have LPS wall either.
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flagella
- Flagellin protein, used for motility (chemotaxis).
- "H" antigen (antigenic)
- surface arrangement can vary (0, 1, 2, to all over surface)
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pili (fibriae)
- promote adherence
- bacteria to bacteria or bacteria to host cell
- "F" antigen
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capsule
- polysaccharide or protein
- antigenic -- "K" antigen
- slime layer = loosely adherent capsule
- often antiphagocytic
- barrier to toxic hydrophobic (detergents)
- synthesis is very energy expensive, only make when necessary
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spores/endospores
- develop inside mother cell under nutrient-limited conditions. Dormant, no metabolic activity, highly resistant to environment.
- Germinate once reach appropriate environment. Dense core with LOTS of layers.
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Fastidious bacteria
- require organic molecules, not just simple building blocks for synthesis of major cellular constituents.
- Can use to diagnose (plates without basic requirements, transmission through environment possible or just host-host)
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microaerophile
- prefer low oxygen levels, can grow without O2
- campylobacter fetus
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indifferent/aerotolerant anaerobe
- ferments in the presence of O2
- strep equii
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facultative anaerobe
- respires with O2, ferments without
- E. coli, staph aureus
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anaerobe (strict)
- killed by O2, ferments without it.
- Clostridium tetani, fusobacterium necrophorum
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aerobe (strict)
- requires O2, can't ferment
- mycobacterium bovis, bacillus anthracis
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campylobacter temperature
likes 45C -- likes it hot!
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listeria temperature
likes 4C, likes it cold (refrigerator okay)
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Plasmid
- autonomously replicating extrachromosomal molecules
- not required for viability
- often encode virulence (TNFalpha inhibition, phagocytosis inhibition) or abx resistence
- insert via transposition (sometimes)
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bacteriophage conversion
- lytic: lyse cell
- lysogeny: integration, cell replication making a "prophage". Integrase integrates into chromosomes, stay forever in generations. Could turn lytic. (botulism)
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pathogenicity islands
- carry many virulence genes
- present in pathogenic strains, messed up or absent in others.
- HUGE, different C+G than host
- associate with tRNA genes or insertion sequences
- often have cryptic mobility genes
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