IMMORTALITY is dead, it was claimed last year, after bacteria were shown to get old and die. That obituary is now looking premature.
Bacteria were long thought to enjoy a sort of immortality, because they simply divide symmetrically into identical daughter cells, neither of which is more likely to contain older components. This sets them apart from multicellular organisms, which contain non-reproductive cells that are doomed to age. Then last year, microbiologists in France found that Escherichia coli bacteria divide asymmetrically, with one daughter cell getting older components than the other. Over many generations, the “older” cells grow more…
