Team:Chiba/Project

From 2008.igem.org

Revision as of 07:19, 26 October 2008

Abstract

Fig.1 Project desgin

"Team : Chiba - E.coli time manager"

　　We control the timing of gene expression by using multiple signaling devices.To this end,we utilize molecules associated with Quorum sensing, a phenomenon that allows bacteria to communicate with each other.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.Although different quorum sensing species have slightly different signaling molecules, these molecules are not completely specific to their hosts and cross-species reactivity is observed [http://www3.interscience.wiley.com/journal/119124142/abstract (1)],[http://partsregistry.org/Part:BBa_F2620:Specificity (2)]. Communication using non-endogenous molecules is less sensitive, and requires a higher signal concentration to take effect.This results in slower activation of receivers.

Introduction

Fig.2 Team logo

Our project

Fig. Our system

従来:消えていく物質の存在時間によって時間調節する。

千葉:常に物質が一定の割合で蓄積されるとき、あるスレッショルド超えるまでの時間を調節する。

調節する方法には、二つが挙げられる。

蓄積するときの割合を変える。

スレッショルド自体を変える

System design

Fig.Project design

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 communication using non-endogenous molecules is less sensitive,and it requires higher signal concentration to take effect.This results in slower activation of receivers.

About Quorum Sensing

　　Quorum sensing is a cell-to-cell signaling action of bacteria. Species of Gram-Negative signaling transfer molecules (so-called autoinducer) is a series of acyl homoserine lactone (AHL). The signals are synthesized by a synthase protein(LuxI-type　proteins) and once they have reached a threshold　concentration,they bound to a transcriptional regulatory　protein(LuxR-type proteins) to induce expression of target genes.

More about Quorum Sensing

• [http://parts.mit.edu/registry/index.php/Featured_Parts:Cell-Cell-Signaling Cell-Cell-Signaling]
  
• [http://www.che.caltech.edu/groups/fha/quorum.html About Quorum sensing]

Controlling the time of a cell-to-cell signaling action

Communication using non-endogenous molecules is less sensitive, and requires a higher signal concentration to take effect.This results in slower activation of receivers.

シグナル分子に対する応答速度を変えるためには３つの方法が考えられる。

1. シグナル分子を作るSenderを変える
2. シグナルを受け取るReceiverを変える
3. シグナル分子自体を分解して、邪魔をする

Signal Molecule Sender

Fig.4 AHL varieties

　English:Each species has their own LuxI-type proteins,which synthesize their specific autoinducers,AHLs.AHLs produced by different LuxI-type proteins differ only in the length of the acyl-chain moiety and substitution at position C-3.Vibrio fischeri has LuxI,which synthesize 3OC6HSL.Pseudomonas aeruginosa has RhlI and LasI,which synthesize C4HSL、C6HSL,respectively.LuxR,which is original for Vibrio fischeri,is activated by its cognate autoinducer,3OC6HSL.However,LuxR is also activated by non-endogenous molecules,C4HSL,C6HSL,and 3OC12HSL.Activation by non-endogenous molecules requires a higher signal concentration[http://partsregistry.org/Part:BBa_F2620:Specificity ⁽²⁾].This results in slower activation of receivers,when AHL concentration is increasing.

日本語:異なる生物はそれぞれに異なるLuxIタイプのタンパク質を持ち、アシル鎖の長さ、あるいはC-3位の置換基が異なる種類のAHLを合成する。Vibrio fischeriはLuxIにより3OC6HSLを、Pseudomonas aeruginosaはRhlIにより、C4HSL、C6HSLを、LasIにより3OC12HSLを合成する(Fig.4).AHLを受け取り応答するLuxRタンパク質はVibrio fischeri由来であり、低濃度の3OC6HSLに対して(~5nM)、応答する。しかし、他種生物由来のAHLに対しても応答することが知られており、より高い濃度のAHLが必要となる[http://partsregistry.org/Part:BBa_F2620:Specificity ⁽²⁾].AHLがゆっくり溜まっていく時、LuxRは3OC6HSLに対して最も早く応答し、他のAHLに対してはそれよりも遅く応答する。

(冨永)

Sender experiments detail

Signal Molecule Receiver

English:

日本語:AHLを合成するSenderだけではなく、AHLを受け取る側のReceiverを変えれば、その応答時間を変えることができる。そこで私たちは、以下のいくつかの方法を考えた。

1. 一種類のSender（AHL<--LuxI）に対して、由来生物の異なるレシーバタンパク質でそれを受信する.
2. レシーバータンパク質であるLuxRに変異を入れることで、AHLに対する応答感度を上下させること.
3. レシーバーのコピーナンバーを変える.

（福冨、小林）

Quorum-Sensing Cross-talk

Table.1 LuxR family gene　Data modified from Fekete et.al. Anal Bioanal Chem (2007)

English:

日本語:

LuxR/Plux mutants show

1. a greater response to 3OC6HSL[http://authors.library.caltech.edu/5553/ ⁽³⁾]
2. a increase in sensitivity to 3OC12HSL[http://mic.sgmjournals.org/cgi/content/abstract/151/11/3589 ⁽⁴⁾].

Copy nomber of Receiver

Receiver experiments detail

Signal Molecule Quencher

AiiAによるAHL分解を同時に起こすことで、AHL供給速度を遅くする.

• AHL reporter with aiiA

Express LuxR and aiiA constantly. AiiA degrades AHL as signaling molecule. Express GFP when the AHL concentration exceed the capacity of aiiA.

This enables the delay of the activation time of receiver.

AiiA experiments detail

Demo Experiments

実験内容とdataかるく

Demo experiments detail

Conclusion

けつろん

Future Work

references

1. [http://www3.interscience.wiley.com/journal/119124142/abstract M.K Winson et al.:Construction and analysis of luxCDABE-based plasmid sensors　for investigating N-acyl homoserine lactone-mediated quorum sensing.FEMS Microbiology Letters 163 (1998) 185-192]
2. [http://partsregistry.org/Part:BBa_F2620:Specificity BBa_F2620:Specificity]
3. [http://authors.library.caltech.edu/5553/ C. H. Collins.et al.:Directed evolution of Vibrio fischeri LuxR for increased sensitivity to a broad spectrum of acyl-homoserine lactones.Mol.Microbiol.2005.55(3).712–723]
4. [http://mic.sgmjournals.org/cgi/content/abstract/151/11/3589 B. Koch. et al.:The LuxR receptor: the sites of interaction with quorum-sensing signals and inhibitors.Microbiology 151 (2005),3589-3602]

• Recent changes
• What links here
• Related changes
• Special pages
• My preferences

• Printable version
• Permanent link
• Privacy policy
• Disclaimers