It's long been believed that some single celled organisms are
basically immortal. Many bacteria divides into two basically
identical "children". In some sense it seems
the original cell was immortal, since there's
a direct line back to the original cell. It
It turns out that bacteria may actually age, as
Stewart, Madden, Paul, and Taddei report
in PLoS Biology.
It turns out that E. coli has a rod structure. When it divides, each daughter gets one pole and then regenerates the other pole. This means that in any given cell, there is one old pole and one new pole. This creates an asymmetry between the daughters of that cell, because one gets the older pole and one gets the newer. Stewart et al. show that the daughter which gets the old pole grows 2.2% slower than the new pole, suggesting that there is some kind of aging going on.
Quite a clever piece of research with a surprising result. If bacteria age, we may be able to use them as a useful model for how people age.
That's very cool. It would also suggest that there are old poles, and really old poles. (What's a pole, anyway?) Some bacs have poles that were created in their mather, and some in their grandmather, some in their great-grandmather, etc. I wonder if old enough poles stop... poling... and if the bacteria eventually can't survive in those branches?
There's some evidence of that, yes:
For more on what a pole is, see http://www.plosbiology.org/plosonline/?request=slideshow&type=figure&sici=journal-pbio-0030045-g001