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Sunday, 13 May 2018 15:59

Maverick Mouse Microbes Mitigate Maladies - BacterioFiles 338

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Published in Bacteriofiles

This episode: Gut microbe transplants from wild mice protect lab mice from disease!

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(9.8 MB, 10.7 minutes)

Show notes: 

bf338housemouseMicrobe of the episode: Cabassou virus

News item

Journal Paper:
Rosshart SP, Vassallo BG, Angeletti D, Hutchinson DS, Morgan AP, Takeda K, Hickman HD, McCulloch JA, Badger JH, Ajami NJ, Trinchieri G, Pardo-Manuel de Villena F, Yewdell JW, Rehermann B. 2017. Wild Mouse Gut Microbiota Promotes Host Fitness and Improves Disease Resistance. Cell 171:1015-1028.e13.

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Episode outline:

  • Background: Studying microbiota in animals immensely helpful
    • Lots of things can be done not possible elsewhere
    • Like last episode
  • But gotta keep limitations in mind
    • Ep 186, mouse microbes different in different rooms of building
  • Mice generally kept with somewhat artificial microbiota
    • Called SPF, specific pathogen-free
    • Or even germ-free, no microbes at all
  • Good for studying what effects microbes CAN have, but practical effects in real world?
  • What’s new: Now, scientists publishing in Cell have discovered that the wild microbes wild mice have in the wild really make a difference in the health of the mice!
  • Methods: Lab mice derived from house mice and other subspecies
    • Mus musculus domesticus from Maryland
    • Mostly lives in woods and fields, moves into buildings sometimes when cold
  • Scientists trapped 800 in horse barns around Maryland and DC
    • Narrowed down to 98 by maturity, species, etc
    • Compared to 21 populations worldwide; these are closest to lab animals
  • Analyzed gut microbes from mice
    • Clustered together, even mice from different barns
    • But significantly different from lab mice
    • Wild had more Bacteroidetes, Proteobacteria, less Firmicutes etc
      • Lab ones have mostly Firmicutes, wild more balanced though
  • Screened wild mice for pathogen exposure
    • Found antibodies against normal ones, but no signs of disease
    • Also not found in microbes
  • So took microbes and introduced into germ-free lab mice
    • 1st of 3 doses went into pregnant mice, to see vertical transfer
    • As control, inoculated others with lab communities
  • Controls’ communities were same as normal lab mice
    • So inoculating works
  • Mice inoculated from wild microbes were distinct from each
    • Stable over generations
    • Close to wild but not identical
    • Very different from lab community
  • So what effect of wild community?
    • Challenged each with mouse-adapted influenza
    • Only 17% of lab microbe mice survived
    • 92% of wild microbe mice
    • Also less weight loss, lower viral titers, less organ damage
  • Also tested with other disease: gut tumors induced by mutagen and inflammation
    • Chemical azoxymethane and dextran sodium sulfate
    • Wild microbe mice had less weight loss, fewer and smaller tumors
      • Also less invasive
  • Summary: Lab mice with gut microbes from wild mice more resistant to infection and even inflammation-associated cancer than if they have normal lab mouse microbes
  • Applications and implications: Study these mice in more detail
    • Learn about how microbes can contribute to these health effects
  • Make mouse models more reliable in general, more representative
  • What do I think: Why I always feel need to mention mouse study
    • Just not safe to assume extrapolation
    • Possible a lot of results in mice are just artifacts of lab conditions
  • Amazing to see how much difference gut community can make
    • Some, like Dr. Martin Blaser, are concerned
    • Are we humans making ourselves like lab animals?
      • Overexposure to antibiotics and other antimicrobial chemicals
      • Deplete important microbe communities and become less healthy
    • Too much extrapolation, of course, but worth considering when possible
    • Hard to replace microbes specific to us if lost from population
      • Need to develop more harmony with microbial world
Last modified on Sunday, 13 May 2018 16:40
Jesse Noar

Jesse Noar is microbiologist with a PhD from North Carolina State University and Bachelor's from Cornell. Most of his research has focused on the amazing abilities and potential uses of bacteria, especially those found in soil. Jesse hosts the BacterioFiles podcast highlighting the most interesting recent microbiology research on all kinds of different microbes, part of the ASM family of podcasts. Learn more at asm.org/bacteriofiles or at www.bacteriofiles.com.

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