Bacterial aging

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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.

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2 Comments

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:


Another long-term effect of aging is the probability of survival of the organism over time. During the growth of the microcolonies, sixteen cells were observed to cease growing; these cells never resumed growth during the course of the experiment. We have defined these cells as potentially dead cells and have analyzed their locations in the lineages. While these apparent deaths may ultimately be due to stochastic events, they show a statistically significant bias (p = 0.01; see Materials and Methods) toward increased divisions spent as an old pole (over the total observation history). This observation is consistent with the hypothesis that aged cells are more susceptible to harmful events and/or less likely to survive them. It is unlikely that these cells represent a growth arrested “persister” state, as it has recently been demonstrated that persister cells that arise during exponential growth occur at a frequency of approximately 1.2 × 10−6 [14]; the appearance of apparently dead cells in our study (about 4.6 × 10−4) is almost 400 times more frequent.

For more on what a pole is, see http://www.plosbiology.org/plosonline/?request=slideshow&type=figure&sici=journal-pbio-0030045-g001

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