long-term monitoring of bacteria undergoing programmed population control in a microchemostat
DESCRIPTION
Long-Term Monitoring of Bacteria Undergoing Programmed Population Control in a Microchemostat. Frederick K. Balagaddé, Lingchong You, Carl L. Hansen, Frances H. Arnold, Stephen R. Quake. Science , 309:137-140 (2005). Article critique presented by Véronique Lecault - PowerPoint PPT PresentationTRANSCRIPT
Long-Term Monitoring of Bacteria Undergoing Programmed Population Control in a Microchemostat
Frederick K. Balagaddé, Lingchong You, Carl L. Hansen, Frances H. Arnold, Stephen R. Quake
Article critique presented by Véronique Lecault
January 10, 2006 EECE 491c
Science, 309:137-140 (2005)
EECE 491c Balagaddé et al. (2005) Science 309:137-140 2
Microfluidics: A Small World with Large Applications…
Protein crystallization
DNA amplification
Electrophoresis
Immunoassays
DNA microarrays
Cell sorting and analysis
(Thorsen et al., 2002)
EECE 491c Balagaddé et al. (2005) Science 309:137-140 3
Scaling Bioreactors Down to Nanoliters…
11x10-31x10-61x10-9 1x103 1x106 1x109 Liters
Advantages:
• Reduced reagent costs
• High-throughput experiments
• Cell tracking
• Reduced waste
• Increased speed of experiments
EECE 491c Balagaddé et al. (2005) Science 309:137-140 4
How do we culture cells?• Batch
• Fed-batch (semi continuous)
• Chemostat (continuous)
Time
Num
ber
of b
acte
ria
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Bacteria and biofilms
(www.medicdirect.co.uk)
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Bacteria and biofilms
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The Microchemostat
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The Microchemostat
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The MicrochemostatExperiment Medium [ glucose]
(M)[bacto-
tryptone] (g/L)
Temperature (oC)
Dilution rate (h-1)
1 MOPS EZ 1.1 -- 32 0.34
2 MOPS EZ 0.11 -- 32 0.30
3 LB -- 0.5 21 0.24
4 LB -- 0.5 21 0.30
5 LB -- 3.0 21 0.37
6 LB -- 0.5 21 0.37
7 LB -- 0.1 21 0.37
EECE 491c Balagaddé et al. (2005) Science 309:137-140 10
The Microchemostat
3 g/L
0.5 g/L
0.1 g/L
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Quorum Sensing
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Quorum Sensing
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Quorum Sensing
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Quorum Sensing
IPTG -
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Quorum Sensing
IPTG +
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MC4100Z1 Cells
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Top10F’ Cells
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Loss of Regulation
MC4100Z1
Top10F’
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Population dynamics
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Population dynamics
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Conclusions
• Operation of a miniaturized bioreactor 300 times smaller than the previous microfermentor.
• Automatic culturing and monitoring of populations of 100 to 10000 bacteria with instantaneous cell resolution.
• In theory, the mutation rate should be reduced by a factor of 105 and
prolong monitoring of homogeneous populations.
• Monitoring the programmed behavior of bacterial population for hundred of hours despite strong selection pressure.
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Critique Summary
To be improved Good
Ma
jor
po
ints
Min
or
po
ints
•Experiments missing to explain what causes the loss of regulation
•Could fit the model to data in order to estimate the true constants
•Could put more emphasis on the absence of biofilm formation and on the limitations of the chemostat
•Should compare mutation rates to a macroscale chemostat instead of a microscale batch
•Very novel technology
•Attempt to show a possible application
•Honesty of the authors
•Clear representation of the microchemostat technology
•Some figures are not very intuitive to read
•Explanation missing for the morphological behavior
•Incomplete Material and methods section leading to hardly reproducible experiments