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22 Cards in this Set
- Front
- Back
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What is the medical significance of bacteria?
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- They are the cause of much morbidity and mortality
- Preventable - Treatable - Can be acquired in hospitals |
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What are the characteristics of bacteria?
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- Prokaryotes
- Very small (0.1-10um, typically 1um) - Highly adaptable - Free living - Motile - Asexual reproduction |
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What is the structure of bacteria?
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In the cytoplasm: nuceloid & ribosomes
Cell envelope (Cytoplasmic (cell) membrane, peptidoglycan layer (cell wall) & outer membrane) External structures |
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Nucleoid of bacteria?
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- single chromosome
- loosely packed - double stranded DNA - no nuclear membrane |
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Ribosome in bacteria?
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- Involved in protein synthesis
- Loose within the cytoplasm |
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What is the cell envelope?
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- Barrier around cell
- Has up to three layers - Cytoplasmic (cell) membrane - Peptidoglycan cell wall - Outer membrane (gram-negatives only) |
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What is the cytoplasmic membrane?
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- Lipid bilayer, similar to eukaryotes
- Involved in energy production - Transport of molecules in and out of cell |
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What is the peptidoglycan layer?
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- The 'cell wall'
- Very thick in gram-positives - Provides structural rigidity - Many immunogenic molecules, teichoic acids & lipotichoic acids |
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What is the outer membrane?
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- In gram-negatives only
- Systems for transport of molecules in and out of cell - Permeability barrier for large molecules - Protects cell - Highly immunogenic (contains much lipopolysaccharide (LPS)) |
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What are the external structures?
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Not all bacteria have external structures
Include: - fimbriae (pili) (typically on gram-negative bacteria) - capsule - flagella |
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What are fimbriae and pili?
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- Hair-like protein structures
- Virulence factors are attached - Fimbrae allow attachment to human cells and bacteria - Sex pili allow attachment to other bacteria for DNA transfer |
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What is the capsule?
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- Loose polysaccaride or protein layers
- Phagocytes can't digest as is a poor antigen - Assists in adhesion to human cells & other bacteria |
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What are flagella?
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Long, whip-like structure. It spins in a 'corkscrew' motion allowing motility.
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How are bacteria named?
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Linnaen system -
Genus species (in italics) |
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How can bacteria be identified?
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- Cell envelope structure (gram-positive or gram-negative)
- Atmospheric requirements - Temperature requirements - Growth speed - Metabolic products - DNA |
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What is the gram stain?
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Identifies cells as gram-positive or gram-negative
Gram-positive = dark purple/blue Gram-negative = pink/red |
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What are the shapes of bacteria?
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- Coccus
- Coccobacillus - Vibrio - Bacillus (rod) - Spririllum - Spirochete |
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How are cells arranged?
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- Single
- Di = 2 - Stepto = many in chain - Staphylococci = many coccus in clump - Pallisade = many bacillus in clump |
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How are cells identified according to atmospheric requirements?
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- Obligate aerobe (like air)
- Obligate anareobe (dislike air) - Facultative anaerobe (mostly like air) - Microaerophile (like to be near-ish to air) - Aerotolerant (don't mind :) |
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What are virulence factors?
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Virulence factors are molecules expressed and secreted by pathogens, important in pathogenesis.
Often bacteria will have multiple virulence factors They can be structural or secreted. |
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What are some examples of structural virulence factors?
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- Capsule
- Flagellum - Pili - Spores (can survive VERY well - chemicals, heat/cold, desiccation, starvation, etc. Germinate when time/conditions are right) |
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What are secreted virulence factors?
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- Biofilm forming compounds (adhere bacteria to surfaces, protect from immune system, antibiotics, etc.)
- Endotoxins (lipopolysaccharide) (on outer membrane of gram-negatives, scan be secreted in 'blebs', antibodies attach to blebs, very immunogenic) - Exotoxins (protein toxins) |
