Microbes age, microbes get fat…
The division of a bacterial cell leads to the appearance of two daughter cells, subsequently giving rise to four cells, each of which also divides – and so on indefinitely. For a long time, experts have been of the opinion that the result of this is the eternal youth of the bacterial population. In other words, it was believed that bacteria never age, or at least do it differently than other organisms.
However, the results of a study conducted by evolutionary biologists from the University of California, San Diego, working under the guidance of Professor Lin Chao, call this paradigm into question. They point out that bacteria actually age and that the ability to age allows them to improve the results of the evolutionary process by unequal distribution of damaged biological material between daughter cells.
Aging of the body is caused, among other reasons, by the accumulation of non-genetic damage, such as irreversibly oxidized proteins. The researchers' computer analysis of the results of two experimental studies published in 2005 and 2010 showed that in the process of division, the maternal bacterial cell moves almost all the damaged molecules into one of the daughter cells, which leads to its "revival" in the form of a second daughter cell, freed from the burden of minutes or hours lived. Interestingly, initially the results of a study published in 2005 were recognized as evidence in favor of the existence of bacterial aging, whereas the results of a 2010 study conducted with the help of more sophisticated experimental equipment, on the contrary, testified to the eternal youth of bacterial populations.
Cartoon about the 2005 articleAccording to Professor Chao, a detailed analysis of the results of both studies showed that, in fact, they demonstrate the same pattern.
The processes of aging and rejuvenation of the bacterial population occur simultaneously and, depending on the assessment method used, the results of their study may lead to false conclusions.
As part of a separate experiment, Professor Chao's group captured the process of dividing populations of E. coli (Escherichia Coli) over hundreds of generations. Analysis of the video image showed that each time an elongated bacterial cell divides into two daughter cells, which subsequently grow and lengthen until they acquire a characteristic elongated shape, but at different speeds. This is also indirect evidence that the growth of one of the cells is slowed down by the inherited "cellular garbage".
Chao explains the advantage of asymmetric division using the example of monetary investments. Let's say you can invest $1 million at 8% per annum or divide it into 2 equal parts and invest one at 6% and the second at 10% per annum. A year later, both methods would bring almost the same income, but after 2 years, the profitability of the second approach becomes obvious.
Bacteria use a similar technique, apparently developed in the course of evolution. If the division of bacteria was symmetrical, the concept of aging would not be applicable to them, but evolution has chosen a more rational approach: due to the aging of one of the daughter cells, the second begins life almost from scratch.
Article by Camilla U. Rang et al. Temporal Dynamics of Bacterial Aging and Rejuvenation is published in the preliminary on-line version of the journal Current Biology.
Evgeniya Ryabtseva
Portal "Eternal youth" http://vechnayamolodost.ru based on the materials of the University of California, San Diego: Do Bacteria Age? Biologists Discover the Answer Follows Simple Economics.
28.10.2011