When a bacterial cell divides into two daughter cells and those two cells divide into four more daughters, then 8, then 16 and so on, the result, biologists have long assumed, is an eternally youthful population of bacteria. Bacteria, in other words, don't age -- at least not in the same way all other organisms do.
But a study conducted by evolutionary biologists at the University of California, San Diego questions that longstanding paradigm. In a paper published in the Nov. 8 issue of the journal Current Biology, they conclude that not only do bacteria age, but that their ability to age allows bacteria to improve the evolutionary fitness of their population by diversifying their reproductive investment between older and more youthful daughters. An advance copy of the study appears this week in the journal's early online edition.
"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 betterto 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' answerthat 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. Those studies, published in 2005 and 2010, attempted unsuccessfully to resolve the question of whether bacteria aged. While the 2005 study showed evidence of aging in bacteria, the 2010 study, which used a more sophisticated experimental apparatus and acquired more data than the previous one, suggested that they did not age.
|Contact: Kim McDonald|
University of California - San Diego