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Team:Harvard
From 2009.igem.org
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Abstract Optical communication is central to interactions between many multicellular organisms. However, it is virtually unknown between unicellular organisms, much less between unicellular organisms of different kingdoms of life. Our team has constructed a system that allows for interspecies, bacteria-to-yeast optical communication. In this system, bacteria to communicate to yeast the presence of IPTG, which results in transcription of lacZ in the yeast cells. To permit bacteria to send an optical signal, we expressed in E. coli a red firefly luciferase under IPTG induction. To allow yeast to receive the signal, we used a two-hybrid-system based on the interaction between the red-light-sensitive Arabidopsis thaliana phytochrome PhyB and its interacting factor PIF3. Interaction between PhyB and PIF3 is induced by the red light from the bacteria, resulting in transcription of the lacZ gene. This is an excellent demonstration of the principles and potential of synthetic biology: this system enables us to optically bridge a physically separated canonical lac operon using light as a trans-acting factor, communicated between the species of cells using optical signals. In other words, we have been able to separate the de-repression and gene expression into two separate cells, bridging this physical separation with light based signals between the cells. The bacteria signal to yeast that the operon has been de-repressed using bioluminescence from the luciferase enzyme. In response to this optical signal, the yeast completes the operon’s function and expresses beta-galactosidase. Importance of optical communication Optical communication is any form of communication which uses light as a means to transmit a message. In a biological context, this means any case where one organism sends a message to another organism using a visual signal, be it color, gestures, or even smoke signals. While optical communication between multicellular organisms is exceedingly common, it is virtually unknown between unicellular organisms. In light of this deficiency, our team decided to create an optical communication system between bacteria and yeast. Not only are these both unicellular organisms, they are from entirely different branches of the tree of life: one is a prokaryote, one a eukaryote. One is a bacterium, the other a fungus. Using the principles of synthetic biology, we were able to design a system allowing these wildly disparate organisms to communicate via bioluminescent signals. Applications of optical communication: Bridging the lac operon The lac operon is one of the first genetic regulatory systems introduced to students of molecular biology: it is the poster-child for complex gene regulation in prokaryotes. The purpose of the lac operon is that it encodes the genes that allow bacteria to break down lactose. In the absence of lactose, transcription of the lactose-digesting genes is inhibited by a repressor. However, in the presence of lactose, expression is de-repressed. In other words, transcription is able to happen in the presence of lactose. As a result there is production of beta-galactosidase, the primary lactose-digesting enzyme. In nature, all of these events happen within the same cell. However, with the techniques of synthetic biology we can do something very interesting with the operon: we can separate the de-repression and gene expression into two separate cells, bridging this physical separation with light based signals between the cells. In these experiments, we have designed a system where bacteria signal to yeast that the operon has been de-repressed using bioluminescence from the luciferase enzyme. In response to this optical signal, the yeast complete the operon’s function and express beta-galactosidase. |
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