Team:Chiba/Project

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The Project


Delay Switch


Parallel Activation


Series Activation

E.coli Time Manager Since 2008


Introduction

決められた時間の長さを生物が認識する機能作りは、生物工学において切望されてきた。例えば物質合成や物質感知などの優れた生物機能を時間制御することができれば、ドラッグデリバリー(定めた時間に薬となる有効成分を私たちの体内でださせる)や健康診断(定めた時間に体内の有害物質濃度を感知できれようになる)活かすことができるだろう。 しかし細胞毎の時間制御ができたとしても、集団で発揮させることができなければ、時間制御の効果は薄くなるのではないか。そこで、私たちは、「生物が集団で発揮するタイマーシステム」を作ろうと考えた。


It has been demanded in biological engineering that making the function that organisms sense the passage of time. We can utilize the excellent functions of organisms such as material synthesis or sensing as


when these functions have been time-controlled as we like.

Project Design

シンクロシステムのいらない、同一系内で使える数種類のタイマーを作るために、私たちは以下の様なデザインを考えている。

対訳: For making some timers without need of synchronizer system and that can be used in a single system we try to make following design.


複数細胞の同時コントロール

時間を扱った2008年のMelbourneや、2007・2008年のParisチーム、2008年のNYMUチームのプロジェクトでは、細胞集団の振る舞いを同時にするためにシンクロシステムが必要だった。そこで千葉はシンクロシステムを使わずに複数の細胞を同一のタイミングでコントロールできるシステムを作ろうと考えた。ここで使うのが細胞間のSignaling Systemだ。このSignaling Systemによって系内の何万モノ細胞に、「感じている時間」を共有させることができるようにしている。

Signaling System

In this project, we use acylated homoserine lactones (AHLs), signaling molecules used for [http://en.wikipedia.org/wiki/Quorum_sensing quorum sensing] in gram negative bacteria. Senders express LuxI or similar enzymes, which catalyze the production of AHLs, under the control of a constitutive (Tet) promoter. Each cell thus generates AHL more or less at a constant rate. AHL can freely permeate cell membranes and are detected by neighboring cells. Receivers constitutively express LuxR proteins (or a similar ortholog), the protein that detects AHL concentrations. When AHLs bind LuxR proteins, the AHL-LuxR complex activates the Lux promoter. The threshold [AHL] at which switching occurs is determined by the affinity of AHL for the particulr LuxR ortholog. about quorum sensing)

Constructing A Delay Switch (Since 2008)

We are constructing delay switches to control/preset the timing of target gene expression. Our project uses two classes of bacteria: senders and receivers. Senders produce signaling molecules, and receivers are activated only after a particular concentration of this molecule is reached. The combinatorial use of senders/receivers allows us to make a‘switching consortium’which activates different genes at the preset times.

Constructing A Delay Switch, Multiple Ways

In principle, there are three ways to delay the activation of chemical communications;

  1. Silencing the Speakers: Rate of signal accumulation down-regulated, for instance, by slowing down the signal generators.
  2. Desensitize Receivers: Switching threshold elevated, for instance, by using insensitive receiver/ reporter systems.
  3. Partial Blocking: Decreasing the by chewing the signal up.

Inter-species communications!

We decided to go for the strategy inspired by Japanese-classic experience; Whenever we speak to somebody in English, we often experience a certain delay in activating the communication. We though this is exactly what we pursued in. See Exp #4. Same applies to the reverse, too. When somebody speaks to us, we definitely need some time (sometime infinite) to get activated. This is all in spite that he/ she was loud and clear enough. The less affinity (perception) we have to English, the longer we need to activate them.See exp #5.

-> Get more information about a Delay Switch!

Constructing A Flow of Activation

We are trying to make a platform for generating an animated pictures using series of new timer cells we have constructed. '07のMissouri Minersや'08の私たちのプロジェクトは、シンクロシステムの必要がないタイマーを作ることに成功しましたが、1種類の系では1種類のタイマーしか使えないという欠点がありました。私たちは同一系内で複数のタイマーの起動をさせようと考えています。

この欠点を補うために考えたのがMutantを利用したParallel Activation Systemと、Crosstalkがおこらない組み合わせを利用したSeries Activation Systemです。


Parallel Activation

Parallel Activationとは数種類のLuxR Mutantを使ったシステムである。 別々のLuxR Mutantが入った細胞を、同時に培養し、蛍光蛋白を順々に発現させようというものである。 異なる種類の細胞タイマーを同時に起動させるということから、私たちはこのシステムをParallel Activationと呼んでいる。

対訳: The Parallel Activation is a system that uses several varietys of LuxR Mutants. The Cells containing different Mutants that is differ each other by virtue of time of responce are cultured in one same system and express the fluorescent proteins in turn. We call this system "Parallel Activation" because of using various Mutants concurrently.


-> Get More Information about "Parallel Activation"

Series Activation

Series Activationでは、数種類の細胞通信機構を使う。最初のスイッチで1種類の通信分子が分泌され、その分子による細胞通信が起こると、通信が起きた細胞は蛍光蛋白と先ほどとは別の通信分子を発現する。別の細胞がその分子を受けり、新たに別の蛍光蛋白と別の通信分子を発現する・・・の繰り返しを起こさせようというものである。Parallel Activationはいわば、細胞を使った伝言システムである。

対訳: We use several types of cell-cell signaling system for Series Activation. At the first switch, a signal molecule is secreted. When the signaling by the molecule occurs, cells that received the molecule express a fluorescence protein and next different signaling molecule. Then next cells receive second molecule and express another fluorescence protein and third signal molecule. Continuing such processes, we meke time-delay syssem for timer. Parallel Activation system is, so to speak, a "whisper down the lane" system.

-> Get More Information about "Series Activation"

Conclusions