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."