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MICRB 265 General Microbiology

MICRB 265 General Microbiology. Doug McFarlane Lecture 10 –Normal Microflora. Announcements. Another sample midterm exam – on website. Last Lecture. Streptococcus pyogenes Helicobacter pylori Normal microflora Skin G.I. tract Oral cavity Stomach Small intestine.

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MICRB 265 General Microbiology

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  1. MICRB 265 General Microbiology Doug McFarlane Lecture 10 –Normal Microflora

  2. Announcements • Another sample midterm exam – on website

  3. Last Lecture • Streptococcus pyogenes • Helicobacter pylori • Normal microflora • Skin • G.I. tract • Oral cavity • Stomach • Small intestine

  4. Gastrointestinal Tract

  5. Today’s Lecture • Normal microflora • Large intestine

  6. Large Intestine • pH nearly neutral (~7) • Anaerobic (strict and facultative anaerobes) • 500-1000 species • Strict anaerobes • Bacteriodes spp. – 1010-1011 cells/g • Facultative aerobes • E. coli – 107 cells/g

  7. Large Intestine • Fecal indicator organisms – Lab 8 • E. coli, Enterococcus faecalis • Flora changes somewhat with diet • Fairly constant – can ID a person by their “poo print” • Gerald Tannock, U of Otago, NZ • Many benefits, some drawbacks

  8. Benefits of Intestinal Microbes

  9. Benefits of Intestinal Microbes • Protection from pathogens • Provide some nutrients/vitamins • Aid in digestion of complex carbohydrates • Modifications to steroids • Stimulates the immune system • Required for normal development of gut epithelial cells The Gut: Inner Tube of Life; Science, Mar. 25, 2005

  10. Probiotics • WHO: “Live microorganisms which when administered in adequate amounts confer a health benefit on the host” • E.g. Lactic acid bacteria • Metabolism  acid (pH ~ 3-4) • Food tastes sour, but inhibits potential pathogens • E.g. Lactobacillus, Bifidobacterium Poo pellets…

  11. Probiotics • E.g. Prevention of food spoilage • Lynn McMullen – UofA • CanBiocin • Cut meat  inoculate  allow for colonization  acid  vacuum seal  anaerobic • Slows spoilage by competition, pH, bacteriocins • E.g. Post-antibiotic therapy – to restore normal flora

  12. Bug #11 - Lactobacillus acidophilus • Bacteria; Gram positive bacillus • S-layer promotes adherence to gut • Lactic acid bacterium (LAB) • Habitat: human gut, genitourinary tract • Antibiotic treatment  yeast infection

  13. Bug #11 - Lactobacillus acidophilus • Babies born by caesarean  more tooth decay… • Acidophilus milk • Yogurt • Probiotics

  14. Prebiotics • Food additives that promote the growth of beneficial bacteria • Usually polysaccharides that promote LAB in the gut

  15. Antibiotics • Can lead to opportunistic infections • E.g. Clostridium difficile • Normally out-competed • Spore-forming • Causes severe colitis • GI tract as reservoir for antibiotic resistant bacteria

  16. Respiratory Tract

  17. Respiratory Tract • Upper – mucous membranes • Mostly bacteria associated with the skin and mouth • E.g. Staphylococcus, Streptococcus • Lower – trachea, bronchi, and lungs • Normally sterile • Ciliated epithelia cells constantly sweep particles upward

  18. Next Lecture • Microbial Diversity • Oxygen requirements

  19. Bug Review

  20. #1 – E. coli

  21. #2 - Methanocaldococcus jannaschii • Archaea • Extreme thermophile • Barophile • N-fixer

  22. #3 - Thiomargarita namibiensis • Huge prokaryote! • Aerotaxis (buoyancy control) • Interesting metabolism

  23. #4 - Mycoplasma spp. • No cell wall • Obligate pathogen

  24. #5 - Streptococcus mutans • Dental caries • (tooth decay) • Capsule, biofilm • Lactic acid bacteria

  25. #6 - Magnetospirillum magnetotacticum • Magneto- and aerotaxis • Amphitrichous

  26. #7 - Myxococcus xanthus • Gliding motility • Social behaviour • Fruiting bodies • Myxospores – differentiation • E. coli hunter • Antibiotic producer

  27. #8 - Pseudomonas aeruginosa • Lophotrichous • Opportunistic pathogen – burn infections; CF • Antibiotic resistance • Metabolic diversity

  28. #9 – Streptococcus pyogenes • Some strains are facultative pathogens • Exotoxins determine type of disease • Strep throat • Scarlet fever • Necrotizing fasciitis

  29. #10 – Helicobacter pylori • Gastric and duodenal ulcers • Example organism with multiple virulence factors

  30. #11 – Lactobacillus acidophilus • Acidophilus milk • Yogurt • Probiotic • Lactic acid bacteria

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