Download VARIED STATE EXPRESSIONS Allen Lin Caltech iGEM 2008

VARIED STATE
EXPRESSIONS
Allen Lin
Caltech iGEM 2008 Brainstorming
Why?
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Currently standard to detect the expression of a
gene: attach GPF in DNA so that it becomes
transcribed and translated as part of a protein.
Can we be more creative?
 What
other types of expressions might bacteria be
able to produce?
Why II?

Can we make the bacteria do something interesting
when it’s in a particular state?
 For
example, make the bacteria have different
phenotypes when
 It’s
in different stages of mitosis ([cyclin])
 Particular operons are active ([free repressor])
 Certain enzyme pathways are activated
Actually…

These two goals are the same
For example….going off topic

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What about have the bacteria make something
when its in a particular state
Say, when a bacteria detects lactose, produces
another compound
And have the bacteria sensitive to the second
compound
… And migrate to the location to the first compound
Compound Detector and Remover
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Bacteria start out in one location
Through random walk, spread across
When a bacterium detects a particular compound A, turns red and
produces a compound B not normally produced by bacteria
Other bacteria in the region have heightened sensitivity to
compound B in chemotaxis; when they detect it, turn green. And they
migrate to the location of the initial bacteria. When they reach
compound A, turn red + green, produce compound B, and digest
compound A
Exponential effect, until compound A is completely digested. Then
the bacteria are no longer red, and disperse through random walk.
No CheZ -> Stationary Cells
Guiding Bacteria with Small Molecules and RNA
Topp, S. and Gallivan, J.P.
J. Am. Chem. Soc., 129, 21, 6807 - 6811, 2007, 10.1021/ja0692480
Use a RNA switch!
Theophylline presence -> mobility
Proof of concept
Problems

Bacteria are completely non-motile when compound
theophylline not present
 Is
there a system in which chemotaxis is turned on by
the presence of a compound, and not mobility is turned
off by the lack of a compound?

Need a high concentration of output compound for
it to diffuse and attract other bacteria
Having gone off-topic…
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Instead of producing GFP when lac operon is
transcribed, produce another compound that the
bacteria secretes different phenotype
When bacteria sense this second compound,
redirect normal chemotaxis scheme
Inputs -> different types of outputs
Uses

So this might be:
 An
efficient toxin clean up system
 An infectious disease recognizer and fighter system
 Anything in which don’t need a lot of resources to
detect, but need a lot of resources to eliminate
Input -> Library of responses

Then that would be okay
 And

highly useful
Here, we have
 Produce
signaling compound
 Produce change in mobility

What else can we do?
 Produce
different phenotype (ex. shiny)
 Interrupt mitosis cycle
 And more