MMI 302: Lecture 12

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  1. Human Microbiota
    • Components of 8 of the 10 vertebrate organ systems appear to have coevolved associations with the microbial world.
    • 1:10 cell number (1013 host cells/1014 bacterial cells)
    • 1:1 gene number (30,000 in 1013/3,000 in 1014)
    • 1:200 gene diversity
  2. Systems with links to Microbiota
    Immune, Circulatory, Digestive, Neuroendocrine, Excretory, musculoskeletal, integumentary, adipose
  3. Interplay between brain and microbiota
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  4. How microbiota is acquired
    • Establishment: Acquired from parent during birth
    • Development: Ecological succession happens, changes to fit the new structure as development happens
    • Stability: Sustained partner exchange and homeostasis, resilience/robustness
  5. Forces that can cause an imbalance
    • Intrinsic:
    • genetic
    • Extrinsic:
    • abiotic-(antibiotics, pollutants, hormones)
    • biotic-invasive species (+/- coevolved)
  6. Model Organisms
    Hydra, Medicinal leech, bobtail squid, zebrafish
  7. Hydra as model species
    • -2 embryonic tissue layers
    •      -surface/gut epithelium
    • -Are colonized by species-specific microbiota
    • -Have antimicrobial peptides
    •      -Hydramacin-1, Arminin-1a, Periculin-2, Kazal-2
  8. Over-expression of perculin-2 in hydra causes:
    • Decrease in abundance of micro-organisms
    • Increase in microbial diversity
  9. Studying microbiota in zebrafish
    • Raise zebrafish larvae +/- microbiota
    • Label fatty acids
    • Use microscope to locate the labeled acids
    • Find that more fatty acids are taken in when + biota
  10. Leeches as model system
    • Contain Aeromonas veronii and Rikenella
    • A. veronii type-3 secretion systems interfere with phagocytosis of A. veronii only
    •       -T3SS mutations show attenuated virulence
  11. Bobtail squid light organ
    • Juvenile light organ have ciliated field that pulls in bacteria
    • Collects all gram - bacteria
    • Vibrio fischeri have two challenges:
    • to become only bacteria in squid, to find way into squid
  12. How A. fischeri enter bobtail
    • Attachment first, Aggregation second
    • Mucus comes out, does something to peptidoglycan
    • V. fischeri chemotaxis into host tissues by sensing chitobiose (most common in pores/ducts in mucus)
    •       -must be primed by squid
    •       -This whole process must exist for colonization
  13. How A. fischeri enter bobtail condensed
    • Host secreted chitin mucusV. fischeri attaches to host cilia, chitinase upregulated from attachment, other antimicrobials upregulated
    • Chitinase activity develops chitobiose gradient, other gram - lost
    • V. fischeri cells chemotax into host
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MMI 302: Lecture 12
2013-11-07 18:25:29
MMI 302

MMI 302
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