A major advance in the understanding of aging processes: The Bacterial model
How evolution and chance jointly define cell ageing and population longevity.
Two main explanations, seemingly in contradiction, are often used to describe the ageing processes of living organisms:
- Ageing as a stochastic process of damage accumulation and redundancy reduction;
- Ageing as part of a life-history strategy refined by natural selection.
These two theoretical postulates make quantitative predictions about how ageing increases the probability of death that could be validated experimentally. Although the two theories are not restricted to metazoans, most research on the different ageing processes of living organisms has been focused on animal models. However, using a simple bacteria, Escherichia coli, as a model organism for studying the mechanisms of ageing would have many advantages:
- work on an organism with well-known physiology and potentially short lifespan;
- experiment on clonal populations to neutralize genetic diversity effects;
- Experiment in controlled, homogeneous environment, identical for all experiments.
- follow the entire life cycle of the organisms studied.
- Increase significantly the size of the cohorts followed;
In an article just published in Science Advances, Drs. Yifan Yang, Ariel Lindner and collaborators (INSERM and CRI, University of Paris) describe E. coli ageing dynamics under the prism of both theories of ageing by focusing on the dynamics of death probabilities. They show that the Gompertz law of exponential ageing already observed in humans (and other animals) is also applicable to protozoans such as E. coli bacteria.
The interdisciplinary team developed a novel lab-on-chip approach at the submicron scale for the isolation and observation of thousands of individual bacteria throughout their life in real time (see image). By dissociating the aging rate from age-independent components of longevity, the researchers demonstrated that increasing investment in cell maintenance through the general stress response pathway reduces the ageing rate and influences the distribution of lifespan at the expense of cell growth.
This trade-off between ageing and growth underlies the evolutionary adaptation of aging rates to the bacterial ‘feast or famine’ bacterial lifestyle and environment (see image).
Taken together, the study demonstrates that both natural selection and stochastic physiology are needed to explain ageing processes.This study paves way for new interdisciplinary research opportunities, combining systems biology, evolution biology and population dynamics to expand the results of this study to higher living organisms. It would lead to further understanding of the fundamental mechanism underlying the universal Gompertz signature of ageing.
This study was conducted as part of the Axa Chair for a systems approach to individual differences in longevity.
[Left] Feast-and-Famine Lifestyle of E.Coli
[RIght] (A) Lab-On-Chip cellular array (blue bacteria kept in individual chambers under flow (B) Cellular array – top view (green/red – live/dead cells; white bar scale = 10 microns (C) time series of four cells (D) E.coli survival curve (time in hours). Video available on demand.
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Inserm, the French National Institute of Health & Medical Research is the only public sector research institution in France exclusively dedicated to human health. Under the dual aegis of the Ministries of Health and Research, Inserm has a budget of M€ 957 and employs 15,000 scientists, engineers and technicians all with one shared objective, namely to promote health—by advancing knowledge about living organisms and their diseases, developing innovative treatment modalities and conducting research on public health.
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Resulting from the merger of Paris Descartes and Paris Diderot Universities and the incorporation of the Institut Physique du Globe de Paris (IPGP), the Université de Paris was officially founded on 20 March 2019 by publication of a decree in France’s Official Journal.
One year after earning the “Initiative of Excellence” label, the Université de Paris is the fruit of a joint effort between its founding institutions. It is transforming the higher education landscape in Paris. Paris Diderot and Paris Descartes Universities will continue to exist until 31 December 2019. During this transition period, the organisations will gradually merge. This will particularly impact administrative aspects, where the groundwork is already being laid in anticipation of the upcoming changes.
The new institution’s first major action will be to establish its governance. Gilles Pécout, Chief Education Officer for the Academy of Paris and University Chancellor, has assigned this mission to Françoise Moulin-Civil, who will be the acting Administrator until a president is elected.
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