Varied State Expressions Allen Lin Caltech iGEM 2008 Brainstorming
Why? • 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 • 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 • 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 RNATopp, S. and Gallivan, J.P.J. Am. Chem. Soc., 129, 21, 6807 - 6811, 2007, 10.1021/ja0692480
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… • 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