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Introduction | Project Design ( 1.Affinity Tag | 2.Communication Module | 3.Size Control ) | Making Marimos | Our Goal
Acknowledgements | Team Members | iGEM Chiba Website | メンバ連絡簿

Project Overview

photo. 1 Marimo in the lake
Our iGEM project is to make a Marimo-ish gathering of bacteria. Marimo is a green spherical shaped algae (shown in Fig.1), which is a popular living organism in Japan as a National Treasure because of its beautiful shape and its smoothness.

Introduction: Why We Make a Marimo

Spherical Multicellular Organism!?

When you see a shape in Nature, you will notice whether a sphere, which is absolutely symmetric in 3D, is really stable or not in Nature. In fact, an oil droplet is a sphere in water. Red blood cell in a hypotonic solution shows its shape change to a spherical balloon. However multicellular organisms have their shape different from a sphere except Marimo. Of course, other algae do not show spherical shape, they live on a surface of stone. It is quite intriguing how Marimo remains its spherical shape in a lake!

Our team focuses understanding how such spherical structure can be sustained even when it Is multicellular organisms.

Project Design: How To Make Our Marimo

scheme. 1 Our marimo system.
What we require to our system is as follows:
  1. Affinity Tag.
  2. Communication Module.
  3. Size Control.

Two cells are used in our system: AHL senders and receivers. Senders generates the affinity tags constitutively, while receivers generates them only when they are induced by AHL. The marimo-forming goes like this:

  • Make the sender core by sticking with the affinity tag.
  • Insert the sender core into the receiver culture.
  • The sender core produces AHL, which make the near receivers to generate the affinity tags and GFPs.
  • The affinity tagged receiver sticks with the central sender core. This will continue until the AHL cannnot reach the marimo boundary,
  • When the AHL reached the marimo boundary, the adsorping stops, which makes a finite-sized marimo bacteria.


Experiments Overview

Making Affinity Tags

scheme. 2 The short peptide with six histidine (“His-Tag”) was inserted into the fliC D3 domain.
  1. Make the affinity tag by inserting the his-tag into the flagellar fillament.
    • Chiba check.png Sequence confirmed
    • Chiba check.png Swarm confirmed
    • Chiba check.png Flagella strained with anti-flagella antibody
    • Chiba check.png Phenotype confirmed
    • Chiba check.png Affnity confirmed


Making Communication Module

scheme.3 New parts BBa_I729005.
  1. Making Receivers
    • Chiba check.png AHL > GFP generator (constitutive aiiA) : BBa_T729006
    • Chiba check.png AHL > GFP & aiiA generator : BBa_I729005
    • Chiba check.png Sensitive AHL > GFP generator : BBa_I729004
    • Chiba nocheck.png inverter-aiiA
  2. Making Senders
    • Chiba nocheck.png MetK Sender : Could not deposit to registry


Controlling Size

photo. 2 Improved Receiver.
  1. Improve Sender
    • Chiba check.png Overexpressed the metK (the AHL precursur synthesis enzyme) in the hope to increase AHL synthesis. : Turned out not to work
  2. Improve Receiver
    • Chiba check.png Inserted 2 mutations in LuxR which is known from the paper to increase activity.
  3. Localize AHL
    • Chiba check.png Tested the GFP expression in constitutive aiiA generator receiver : Went too much.
    • Chiba check.png Tested the GFP expression in AHL-induced aiiA generator receiver : Needed to twist the circuit more.
    • Chiba nocheck.png AHL-induced inverter aiiA receiver. Not yet assembled.


Making Marimo

  1. Chiba nocheck.png Moving FliC-His generator. : Not yet assembled.
  2. Chiba nocheck.png FliC-his biobrick : Not yet assembled.


Our Goal

Although we could not reach them, below we describe the goal that we set to make a marimo bacteria.

  • A test of adsorption between flagella
  • A test to confirm a limit of size
  • A test to form Marimo
  • A test of size control

See Details

In the Long Run

See here : our brainstorming of the marimo future!



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