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Operation ECHO
== Why we name after ‘ECHO’? ==
I guess that most of us have heard the Greek mythology of the love between nymph Echo and Narcissus. The voice of Echo remains hovering in the valley in the end of the story, from then on, ‘echo’ starts to have a meaning as reverberation or response. In the field of automation, we use ‘feedback’ to refer the process of response in a system, that is, the process in which part of the output is returned to its input in order to regulate its further output, just as an echo. Analogously, ‘echo’ plays a significant role in our design. CELL-A generates AHLs, sending a message to CELL-B, and after B expresses the particular gene, B will ‘echo’ the message to respond. The ECHO part contributes to the communication and well-function of the system.
What does ‘homochronous’ refer?
The prefix ‘homo’ represents ‘same’, while ‘chrono’ means ‘time-related’. As a jargon of Information, the word ‘homochronous’ describes the relationship between two signals that their corresponding significant instants are displaced by a constant interval of time. Here we use this term to depict the relationship between CELL-A & B. That is to say, in the process of oscillating, the AHL expression rate of CELL-A and that of B (also RED and GREEN fluorescent signals) share the same period, or fluctuate in a same pace. In addition, the interval of two signals remains constant, so the RED signal comes out while GREEN fades away at the same time and vice versa. Consequently, time goes, RED and GREEN flare alternately.
How does the system work?
The Ring Oscillator is a device in digital electronic circuits, and it’s composed of an odd number of NOT gates or inverters attaching in a chain, with the last inverter is fed back into the first. Because of the odd number, the final output is the logical NOT of the first input, and the delay as well as the feedback cause the oscillation. When the idea is applied in the synthetic biology, we use two populations of E.coli to construct a system, in which CELL-B induces A and A restricts B. To explain it an electronic way, CELL- A acts as a NOT gate while B as a transfer gate, forming a feedback network with one (of course is odd) converter, with a delay time of biological reaction. Then, theoretically, the system will oscillate.
