Do bacterial cells get “older” after repeated divisions? What would that even mean, once an original “mother” cell has divided into two “daughters”? Well, there are certain things one might look for as indicators of aging. For example, accumulation of molecular damage and slower rates of division in succeeding generations.
Previous studies have given conflicting results. One one hand it seems that many bacterial cells in later generations do show signs of having aged. But on the other, if aging is measured over the average of the whole population, it isn’t found.
The latest study found that, just as a population genetic model predicted would be optimal, half the daughter cells in a new generation appeared to be young and rejuventated, while the other half had accumulated the signs of aging.
“Aging in organisms is often caused by the accumulation of non-genetic damage, such as proteins that become oxidized over time,” said Lin Chao, a professor of biology at UC San Diego who headed the study. “So for a single celled organism that has acquired damage that cannot be repaired, which of the two alternatives is better—to split the cellular damage in equal amounts between the two daughters or to give one daughter all of the damage and the other none?”
The UC San Diego biologists’ answer—that bacteria appear to give more of the cellular damage to one daughter, the one that has “aged,” and less to the other, which the biologists term “rejuvenation”—resulted from a computer analysis Chao and colleagues Camilla Rang and Annie Peng conducted on two experimental studies.