Bacteria make long protein chains that may be similar to the ancestors of microtubules, structures found in the cells of more complex organisms. Microtubules perform crucial cellular tasks, including pulling chromosomes apart during cell division.

Grant Jensen and Martin Pilhofer at the California Institute of Technology in Pasadena and their team captured cryo-electron micrographs of several species of Prosthecobacter bacteria, which contain multi-protein chains reminiscent of microtubules. These are forged from repeated spiral arrangements of proteins that are evolutionarily related to those in the microtubules of other organisms.

It is not clear what bacterial microtubules do. The authors suggest that the bacteria that gave rise to other, more complex organisms passed on proteins capable of forming microtubules.

PLoS Biol. 9, e1001213 (2011)