E. coli ages

"Until recently, people thought that bacteria cannot age," said Martin Ackermann, of the ETH Zentrum, who was not involved in the study. "Then, we published this paper showing aging in bacteria with asymmetric division. The next question was if a visible morphological asymmetry was necessary or whether all bacteria could age. This new paper suggests that aging can actually be found in all bacterial cells, maybe in all living cells."In the PLoS study, Eric Stewart, of INSERM and Paris 5 René Descartes University, and his colleagues used automated time-lapse microscopy to follow individual bacteria throughout nine subsequent cycles of reproduction and measured several physical parameters in over 35,000 cells. They found that daughter cells that inherited the "old pole" of a dividing parent cell - a pole coming from the previous generation in contrast to one newly formed - had a reduced rate of growth, a reduced rate of offspring formation, and an increased risk of dying, compared to cells inheriting new poles.The team also discovered that although division in E. coli does not show morphological asymmetries, it is characterized by functional asymmetries, which has not been described in this species before. That could be how the organism satisfies one of the requirements of the established hypothesis of aging: only organisms that undergo asymmetric division, and produce offspring that are smaller than the parents and thus need to grow and develop before reproducing themselves, can age. E. coli, however, does not have smaller offspring, nor does it undergo a juvenile phase.Thomas Nystr？m, of G？teborg University, acknowledged that the paper casts some doubt on the idea that E. coli divides in a perfectly symmetrical fashion so that the daughter cells display equal fitness. "However, it appears a bit early to announce that E. coli belongs to organisms exhibiting mandatory replicative aging and that immortality is too costly or mechanistically impossible in natural organism