IGEM:Idea exchange

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Most-wanted parts

Square bacteria

Apparently, there is a bacteria that grows into square colonies. I heard about it from an interview with Sydney Brenner, however after looking pretty hard I can't find any more information about it. he thought it was called tetramitus, but that's an amoebae as far as I can tell. I tried getting a hold of him to see if he remembers what it's actually called, but no luck (getting a hold of him). If you can find it there's probably lots of cool stuff to be done with it. His quote from the interview follows:

Brenner Quote about Square Bacterial Colonies

"As a model of polarity I, I played around in 1965, this is very early, with caulobacter. In fact, I made some mutants of caulobacter. Caulobacter is a bacterium that has a very interesting life cycle which involves a polar, polar growth. That is, one side of the bacterium is different from the other. One side carries a stalk, to which the bacterium attaches, when it divides one of the daughters makes a flagellum and the other one- and, and then when that divides, one of its daughters makes a stalk again. So one has to, one has to say- how does this bacterium know which is its left side and which is its right side? These caulobacters had been discovered by Roger Stanier, who I knew at Berkeley, and so I got some cultures from him and grew colonies and made some mutants, they were nutritional mutants. And the idea was what can we make mutants to control this cycle and use bacteria as a model of differentiation. I also played around with a wonderful bacteria which I think is called tetramitus. This little bacterium that grows in plates. I found it very difficult to grow. It grows as a square plate of bacte- of, of- a square colony, one layer thick. It's a very interesting bacterium, because it means that successive divisions are polarised at right angles to each other. And we did grow some in the lab, and wondered whether this wouldn't be something to work on in order to see how was it that a plane of division in something like a bacterium could in successive divisions be rotated through 90 degrees."

  • he got back to me eventually: "The organism is Lampropedia hyalina and a paper on the division was written by Kuhn and Starr in 1965. -Sydney Brenner"
  • Another square bacteria is Haloquadratum Walsbyi (pointed out by Josh Michener)
    • Another paper on it here: [1]
  • Contact: Jason Kelly (MIT iGEM team)

Helical Bacteria

  • Crescentin is believed to cause Caulobacter to form a helical shape. Disrupting the CreS gene causes the bacteria to revert to a rod shape (necessity). Could importing the gene into E. coli produce the reverse effect (sufficiency)? [2]

Random Number Generator

  • FimE inverts a specific stretch of DNA, defined by a pair of sequence elements (IRR and IRL), forming a DNA loop between the two elements[3]. If we add multiple copies of one of these elements (one IRR, two IRL), would FimE randomly choose one of the sites (one IRL out of the pair) to invert between? Either choose one of several promoters to attach to a given gene, or one of several genes to attach to a given promoter.
  • Then, can we tune the probability (from, say, 60:40 to 80:20 to 20:80)? Ideally do this dynamically (based on some small molecule) - use proteins that bend DNA to affect the probability of loop formation.

Population Variability

  • Slipped-strand mispairing [4] can produce a heritable variation in the expression from a promoter. Roughly one in 1000 divisions produces a change in expression. Couple this expression to a selectable/counterselectable marker. Under any given condition (selection, say), the population thrives, but with a small group of the opposite phenotype (non-expressing). Switch conditions (to counterselecting), and the population can use these revertants to recover.
  • Under constantly varying conditions, most circuits would die. These cells, though, can adapt and pass that adaptation on to their descendants.

Hack some moss

Jason R. Kelly: This moss seems pretty engineer-able. Do something cool with it. Let me know if you do, I'll help if I can :)

Protein sequences and music


  1. Bolhuis H, Poele EM, and Rodriguez-Valera F. Isolation and cultivation of Walsby's square archaeon. Environ Microbiol. 2004 Dec;6(12):1287-91. DOI:10.1111/j.1462-2920.2004.00692.x | PubMed ID:15560825 | HubMed [walsby]
  2. Margolin W. Bacterial shape: concave coiled coils curve caulobacter. Curr Biol. 2004 Mar 23;14(6):R242-4. DOI:10.1016/j.cub.2004.02.057 | PubMed ID:15043836 | HubMed [shape]
  3. Ham TS, Lee SK, Keasling JD, and Arkin AP. A tightly regulated inducible expression system utilizing the fim inversion recombination switch. Biotechnol Bioeng. 2006 May 5;94(1):1-4. DOI:10.1002/bit.20916 | PubMed ID:16534780 | HubMed [fim]
  4. Torres-Cruz J and van der Woude MW. Slipped-strand mispairing can function as a phase variation mechanism in Escherichia coli. J Bacteriol. 2003 Dec;185(23):6990-4. PubMed ID:14617664 | HubMed [phase]
All Medline abstracts: PubMed | HubMed