Immortal bacteria

From http://www.newscientist.com/article/dn10154-ageing-may-be-a-lifestyle-choice-for-bacteria.html

"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 multi-cellular 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 receiving older components than the other. Over many generations, the “older” cells grow more slowly and eventually die (see Bacteria death reduces human hopes of immortality).

Long live immortality

Now, researchers led by Milind Watve at Abasaheb Garware College in Pune, India, have run a mathematical model that simulates the success of cells that develop either symmetrically or asymmetrically. This predicts that whether bacteria age or become immortal may depend on how well fed they are.

Under good growth conditions with lots of nutrients, asymmetric division is favoured because the “old” cells die off but the “young” ones grow faster. When nutrients are scarce, however, symmetric cell division gives better overall survival and growth across both daughters.

“Natural selection can favour symmetric division under certain conditions, so immortality is not dead,” says Watve. "