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Sunday, 01 July 2018 20:08

Super Sonic Cell Sacs - BacterioFiles 345

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Published in Bacteriofiles

This episode: Protein bags of gas in bacteria could help make ultrasound imaging more versatile!

Download Episode
(7.6 MB, 8.25 minutes)

Show notes: 

bf345flosaquaeMicrobe of the episode: Cronobacter virus Esp2949-1

News item

Journal Paper:
Bourdeau RW, Lee-Gosselin A, Lakshmanan A, Farhadi A, Kumar SR, Nety SP, Shapiro MG. 2018. Acoustic reporter genes for noninvasive imaging of microorganisms in mammalian hosts. Nature 553:86–90.

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Episode outline:

  • Background: Microbes have many interesting abilities
    • Try lots of different approaches to adapt to environment
  • One example: gas vesicles in water dwellers
    • Protein sacs that let air in/out but not liquid
    • Fill up with gas to increase buoyancy and float up
    • Easier than swimming; automatic directionality
    • Can regulate oxygen or light exposure
  • What’s new: Now, scientists publishing in Nature have discovered that these gas vesicles can be used in a medical setting: to improve the versatility of ultrasound imaging!
  • Vesicles scatter sound waves better than other things
    • Show up as higher contrast on ultrasound
  • Methods: Engineered Escherichia coli to produce gas vesicles
    • About 100 per cell, ~10% of volume
    • Not enough to generate buoyancy, except for a few
  • Tested with ultrasound pulses
    • Showed good contrast
    • When pressure applied to burst the vesicles, contrast went away
    • Some other engineered cells not optimized for right vesicle size also didn’t show contrast
  • Concentrations of cells from 50 million to 1 billion per mL gave increasing signal
    • Could increase signal even more using only especially buoyant cells
  • Also tried using as a reporter
    • Put vesicle production under control of inducible promoter
    • Added certain chemical, IPTG, cells sensed and produced vesicles
  • Can modify in various ways as needed
    • Number, pressure required to collapse, induction
  • Final test: in vivo
    • Put in mice, in gut
    • Allowed very localized imaging
    • Compared with bioluminescent bacteria, which just showed up somewhere in abdomen
  • Summary: Bacteria producing gas-filled vesicles can be used to improve ultrasound imaging in the body
  • Applications and implications: Could target bacteria to particular place in body to image
    • Cancer, for example, with strains that go selectively to tumors
    • Or particular location where something is sensed
      • Induce vesicle production only there
    • Various creative options
  • Some improvement seems possible with more engineering
  • Could be good for research too, in animals or other places where light doesn't pass through well
  • What do I think: Gotta make sure strain does what we want and not other unwanted stuff
  • But useful to have different options for imaging/diagnostics
    • Fluorescence and bioluminescence have their place
    • But sometimes not enough
  • Clever use of clever microbe environment strategy
Last modified on Sunday, 01 July 2018 20:12
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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