Bacterial Mitosis

I guess prokaryotes are looking more and more like eukaryotes.

It turns out that their DNA is moved around by cytoskeletal filaments. The most recent (and one of the most dramatic) examples can be seen in a recent article in G&D where Fogel and Waldor describe how ParAI polymers yank the DNA around by being attaching to ParBI proteins that are anchored to specific sites called parSI sites. Although ParAI is shares structural features with MreB and thus actin, it is the functional analogue of our microtubules, ParBI would be like our kinetochores and parSI is the equivalent of our centromeric DNA.

To the right is a cartoon model (DNA is the blue line, the parSI site is attached to the ParBI protein which is a blue dot and the ParAI is the yellow polymer). As ParAI depolymerizes (C=>D=>A), ParBI which is thought to bind to the end of the ParAI polymer, gets yanked along. This is analogous to how a kinetochore in our cells binds to a depolymerizing microtubule during anaphase and is thus yank to the either side of a dividing cell. In our cells both chromosomes are yanked apart while here one DNA strand is fixed to a pole while the other strand is whisked off to the new pole. Here are some nice images from a time lapse of this process:

Notice how the ParBI in green follows the comet of ParAI polymer in red.

We are slowly finding many eukaryotic type machines in proks. So what's next? Proks with brains?

Ref:
Michael A. Fogel and Matthew K. Waldor
A dynamic, mitotic-like mechanism for bacterial chromosome segregation
Genes & Dev 20:3269-3282, 2006