4b. Bacteria - 4. Microorganisms as Pathogens: Bacteria...

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    4. Microorganisms as Pathogens: Bacteria
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    2 Prokaryotes as Pathogens Bacterial Survey Survey of Prokaryotes 3 basic shapes Rods - 0.5-20 µm bacillus (bacilli) streptobacilli (chain of rods) Spheres - 0.5 µm coccus (cocci) streptococci (chain of spheres) tetrads and sarcinae (packets of spheres) Spirals - vibrios spirilla spirochetes Inclusions - intracellular bodies
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    3 Bacteria Survey bacilli (E. coli bacillus) club-shaped bacilli (C. diphtheriae) streptobacilli (B. subtilis) bacilli with spores (C. tetani)
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    4 Bacteria Survey diplococci (S. pneumoniae) streptococci (E. faecalis) sarcina diplococci (N. gonorrhoeae)
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    5 Bacteria Survey staphylococci (S. aureus “grape clusters”) spirochetes (T. pallidum) inclusion (Chlamydia) vibrios (Vibrio cholera)
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    6 Bacterial Structures Flagella Flagella locomotion for many species 10-20 µm long, 0.2 µm thick flagella rotate (in eukaryotes they whip) results in corkscrew motion of flagellum can act as an invasin axial filaments: intracellular flagella in spirochetes PF PC OS Outer sheath (OS) Protoplasmic cylinder (PC) Periplasmic flagella (PF)
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    7 Species-Dependent Arrangement of Flagella Structures Monotrichous: single flagellum Lophotrichous: flagellar tufts Peritrichous: flagella surround Amphitrichous: polar flagella
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    8 Bacterial Structures Pili Pili (fimbriae) Pilus (singular) Function : NOT MOTILITY 1. as adhesin attachment and colonization can act as antigen ( antibodies can be made against them) antibodies can block attachment and colonization important avenue of research: develop antibodies to prevent pili attachment of N. gonorrhoeae
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    9 Bacterial Structures Pili Function (continued): 2. in exchange of genetic material ( conjugation )
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    10 Bacterial Structures Pili Conjugation: Pilus attaches Donor and recipient make contact Copy of DNA (F factor) is transferred Recipient becomes new donor sometimes, other genes are transferred
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    11 Bacterial Structures Capsule Capsule (Glycocalyx) a secreted layer of polysaccharides (sugar polymers) and small proteins sticky and gelatinous found on certain cocci and bacilli
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    12 Bacterial Structures Capsule Several functions : buffer between cell and environment protects against dehydration prevents nutrients from flowing away prevents phagocytosis by WBCs (evasin) Streptococcus pneumoniae can be deadly when encapsulated But harmless with capsule removed (virulence factor) virulent avirulent
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    13 Bacterial Structures Capsule can attach bacterium to tissue Streptococcus mutans (dental caries) attaches to teeth with dextran (formed from sucrose) bacteria accumulate metabolic breakdown of carbohydrates to acids acids dissolve enamel
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4b. Bacteria - 4. Microorganisms as Pathogens: Bacteria...

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