Chiba University iGEM07 team's project is to make a Marimo-ish gathering of bacteria. Marimo is a green spherical shaped algae, which is a popular living organism in Japan as a National Treasure because of its beautiful shape and its smoothness. You can read more about marimos below. Our motivations for making Marimo bacteria is as follows.
Why Making "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 using E. Coli. Since E.Coli is unicellular organism, this approach is quite challenging....
Making 3D colonies- for next generation (lazier) molecular biologists
For years microbiologists have been using agar plates to isolate cells from each other. By spreading the diluted cells on a solid surface, we can make "colonies", dome-shaped gathering of genetically identical cells. Although convenient, this is only two-dimentional. What if we can create three dimentional (spherical) colonies with controlled/ defined size? Thus we can eliminate the plating process that everybody hates. Combined with the microfluidics devices, we might be able to pick, isolate, count, or innoculate each of the floating yet independent colonies to conduct routine works in future molecular biology. Crazy thought? Well, that is exactly what our advisors say.
Toward the control the population size of the bacteria community
Even in the bacteria community, sometimes they need to do the population control. This is especially so when we think about the chemical production using bacteria robots.
Besides the above illogical/ unjustified reasons, we think this project leads to the behavior control of the bacterial comunity. Lots of challenge in the project including diffusion control of small/ large molecules, chemical production/ degradation balancing,.....
Actually, the name "marimo" indicates the algae filament, not the sphere. The sphere shape is one of the three growth forms of the aggregated marimo fillaments. Another growth form lives as free-floating fillaments as small tufts of unattached filaments that frequently form a carpet on the muddy lake bottom. The third is epilithic (growing on rocks). Marimos are found in some of the lakes in Japan and other countries, but the beautiful spherical shaped marimos are only known in Iceland, Estonia and Japan.
How Marimos are Made
Spherical marimos are formed through the growth of a core which is a fragment of ancestral marimos. So when you watch the cross section of the spherical marimo, you do not recognize a core-shell structure in it. How about the most ancestral marimos? It is expected that the most ancestral marimos had a core made of inorganic materials such as cray particles or sand solids.
Marimos are a popular "pet" in Japan. Well, you can't keep the National Tresure as a pet, so they house the artificial one instead. Although the mechanism of how the spherical marimo are made is not known in detail, the alternative method of making marimo have been invented from about 30 years ago by many Japanese scientist/botanist/marimoist.
1. 阪井與志雄，マリモの科学，北海道大学図書刊行会, 1991 (Yoshio Sakai, Marimo no Kagaku（"The Science of Marimo"))
2. 中沢信午，マリモはなぜ丸い その生態と形態，中公新書，1989 (Shingo Nakazawa, Marimo wa naze marui ("Why marimos are spherical"))