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From cyanobacteria...
• Photosynthetic
• Circadian rhythm
• Evolved over billions of years
...to E. coli
• Model organism for synthetic
biology
• BioBrick registry
Cyanobacterial Oscillator
Harvard iGEM 2006
Applications of a Bio-oscillator
12PM
12PM
6PM
6AM
12AM
12AM
Time
Cyanobacterial Oscillator
Harvard iGEM 2006
6PM
-Clock
-Nightlight
-Timed drug
delivery
-Bio-circuitry
-Scientific
research
Cyanobacterial
Bio-oscillator
The Repressilator
Lac
λcI
Tet
Elowitz et al. 2000
Fluorescence
`
Time
Cyanobacterial Oscillator
Harvard iGEM 2006
10h
The Kai Clock in Cyanobacteria
P
P
P
P
P
P
Phosphorylation of KaiC
•KaiC autophosphorylates and
dephosphorylates
•KaiA promotes phosphorylation
•KaiB inhibits KaiA
•Transcription-translation independent
•Period: 14-60 h
b
Time
Cyanobacterial Oscillator
Harvard iGEM 2006
Achievements
Goal: reconstitute the cyanobacteria Kai oscillator in E. coli
1. Created KaiA, KaiB, and KaiC BioBricks.
2. Combined the above with registry parts to form functional
BioBricks.
3. Expressed Kai proteins in E. coli and verified interaction.
Cyanobacterial Oscillator
Harvard iGEM 2006
Results: Construct Creation
We’ve made the following constructs:
Kai genes
Lac promoter + Kai genes
KaiA + KaiC and KaiB + KaiC
(with promoters)
Cyanobacterial Oscillator
Harvard iGEM 2006
Results: Protein Interaction
Western blot Image
Anti-KaiC antibodies
• Constructs were transformed in E. coli
• Cultures were grown for 16 hours
• Western blot was washed with anti-KaiC antibodies
(courtesy of Professor Susan Golden at Texas A&M)
Cyanobacterial Oscillator
Harvard iGEM 2006
Results: Protein Interaction
Western blot Image
Anti-KaiC antibodies
P
P
P
P
P
Cyanobacterial Oscillator
Harvard iGEM 2006
P
Results: Protein Interaction
Western blot Image
Anti-KaiC antibodies
P
P
P
P
P
Cyanobacterial Oscillator
Harvard iGEM 2006
P
Results: Protein Interaction
Western blot Image
Anti-KaiC antibodies
P
P
P
P
P
Cyanobacterial Oscillator
Harvard iGEM 2006
P
Results: Protein Interaction
Western blot Image
Anti-KaiC antibodies
P
P
P
P
P
Cyanobacterial Oscillator
Harvard iGEM 2006
P
Further challenges
Phosphorylated KaiC (constant production)
Synchronization problem
• Between cells
• Within cell
Percentage of phosphorylated KaiC
Verify oscillation in E. coli.
1
0.9
0.8
0.7
0.6
0.5
0.4
0.3
0.2
0.1
0
1
25
49
73
97
121
145
169
193
217
Time (h)
Time
Cyanobacterial Oscillator
Harvard iGEM 2006
Output from a computer model simulating KaiC oscillation in a
single cell
Conclusion
Thanks for listening
Harvard iGEM 2006
Acknowledgements
• Our teaching fellows Chris Doucette, Shawn
Douglas, and Nick Stroustrup for their valuable help
in lab
• Profs. Alain Viel, George Church, Pam Silver,
William Shih, Radhika Nagpal, and Jagesh Shah
• Prof. Susan Golden at Texas A&M for providing antiKaiC antibodies and advice
• Peter Wiegele @ MIT and Eric Webb @ WHOI for
cyanobacteria strains
Thanks for listening
Harvard iGEM 2006
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