Binary Fission: The Key to Immortality?
Bacteria differ from us in many ways, including in their modes of growth and reproduction. Unlike humans and other animals, single-celled organisms, such as bacteria and some fungi, can undergo a process called binary fission to reproduce, meaning that they duplicate their DNA and then split in 2.
Replication via binary fission can be very fast—the fastest-growing bacterium we know of can divide in less than 10 minutes!
Indeed, it was long thought that bacteria and other organisms that reproduce via binary fission do not age at all. This was because binary fission was thought to be a symmetrical division, producing a parent and offspring identical in age, thus leading to a what scientists called ‘functional immortality’ for the population. On the other hand, asymmetric division, whereby the parent is older than the offspring, was thought to be required for an organism to be able to age at all.
Evidence against the accepted immortality paradigm first came in 2005, when scientists showed that Escherichia coli actually exhibits differences between ‘old’ and ‘new’ in parent and offspring cells, respectively. By following dividing cells with a microscope, the researchers could show that the older cells’ growth rate and offspring production decline over time, and that they die more frequently than their younger offspring cells. Thus, despite looking the same, the cells undergo divisions that leave them functionally asymmetric, causing cells to age over time.
Time waits for no one, not even bacteria—and that’s a good thing. Far from immortal beings beyond the reaches of aging, bacteria are an interesting system in which to study the molecular mechanisms that contribute to age-related decline.