Navigation Links
Scientists offer way to address 'age-old' questions
Date:9/7/2011

Scientists have devised a method to measure the impact of age on the growth rates of cellular populations, a development that offers new ways to understand and model the growth of bacteria, and could provide new insights into how genetic factors affect their life cycle. The research, which appears in Evolution: International Journal of Organic Evolution, was conducted by scientists at New York University and the University of Tokyo.

When bacterial cells age, their capacity for reproduction is reduced. Individual cells within populations are subject to the force of selection, which results from differences in growth rates. Broadly speaking, growing populations are dominated by relatively young cells. A population's age structure, however, depends sensitively on the interplay between selection and the reproductive capacities of the cells.

The researchers sought to understand how changes in cells' reproductive capacity would affect the population's growth rate. This question dates back to seminal research in population genetics by Ronald Fisher in the 1930s and William Hamilton in the 1960s. Typically, the answer is indirect, and relies on a measured life table and reproductive capacity, which takes into account survival and birth rates.

The NYU and University of Tokyo researchers hypothesized that a more direct gauge would be to examine the bacteria's lineagestheir history over several generations. In other words, they proposed looking backward several generations into the population's tree of cell divisions. This allowed them to directly measure the response of the bacteria's growth rate to age-specific changes in mortality and reproductive capacity.

"The force of selection within populations leaves key signatures in the population's lineage tree," said Edo Kussell, a professor of biology at NYU's Center for Genomics and Systems Biology and the study's corresponding author. "Theory allows us to interpret these in powerful ways. For instance, we found that how frequently a given age is observed along lineages is a direct reporter of how important that age is to the population's growth rate. This would allow us to predict the success or failure of mutant bacteria, which age differently from normal ones."

Using experimental data from laboratory populations of E. coli, the researchers confirmed several theoretical predictions. The article's other co-authors were Yuichi Wakamoto of the University of Tokyo and the Japan Science and Technology Agency and Alexander Grosberg, a professor in NYU's Department of Physics and its Center for Soft Matter Research.

The work builds upon a previously published paper in the Proceedings of the National Academy of Sciences, in which Kussell and co-author Stanislas Leibler of Rockefeller University offered a way to infer the behavior of individual cells from population-level measurements.

One of the behaviors they considered is known as stochastic switching, a strategy in which cells randomly activate certain genes in order to survive. Notably, pathogenic bacteria, which cause disease in both humans and animals, engage in stochastic switching, resulting in alternative cellular states that improve the bacteria's ability to survive. The cells best suited for given conditions survive while others die offanother example of selection within populations. Understanding what prompts this type of cellular change in bacteria, and which strains are more sustainable than others, could then lead to alternative methods to curb bacterial growth.

The study centered on understanding two types of cellular strategiesresponsive switching, in which cells change their state by reacting to environmental change, and stochastic switching, in which cells randomly activate certain genes, independent of external forces. Within a population, however, it is difficult to detect which strategy is being usedwhen cells change behavior, are they responding to their environment or is the change random?

Kussell and Leibler sought to develop a method that could disentangle these strategies. They showed that individual histories of cellstheir lineageswould reveal differences between stochastic and responsive switching.

"Since stochastic switching organisms rely on selection to survive, we expected that if we could measure the strength of selection, we could distinguish the two strategies," Kussell said. "Once again, selection leaves a key signature in the population's lineage tree. In this case, the signature is the variance in cell divisions between lineages. If we measure that, then we can tell which strategy the cells are using internally."

The researchers simulated bacteria growing under fluctuating environmental conditions, and applied their lineage-based tests. This allowed them to show that the lineage tree indeed contains sufficient information to distinguish the two cellular strategies.

The importance of stochastic switching has recently been demonstrated in populations of cancer cells. With improved lineage tracking tools for cancer cells, it may soon become possible to apply some of the ideas that Kussell and co-workers have been developing in the bacterial context, also in other systems, such as tumor and stem cell populations.


'/>"/>

Contact: James Devitt
james.devitt@nyu.edu
212-998-6808
New York University
Source:Eurekalert

Related biology news :

1. Jefferson scientists deliver toxic genes to effectively kill pancreatic cancer cells
2. Scientists identify novel inhibitor of human microRNA
3. Argonne scientists peer into heart of compound that may detect chemical, biological weapons
4. MU scientists go green with gold, distribute environmentally friendly nanoparticles
5. Scientists identify gene that may contribute to improved rice yield
6. Scientists discover why a mothers high-fat diet contributes to obesity in her children
7. MU scientists see how HIV matures into an infection
8. Earth scientists keep an eye on Texas
9. Thinking it through: Scientists call for policy to guide biofuels industry toward sustainability
10. Scientists identify a molecule that coordinates the movement of cells
11. Scientists Find new migratory patterns for Mediterranean and Western Atlantic bluefin tuna
Post Your Comments:
*Name:
*Comment:
*Email:
(Date:4/5/2017)... LONDON , April 4, 2017 KEY ... is anticipated to expand at a CAGR of 25.76% ... neurodegenerative diseases is the primary factor for the growth ... full report: https://www.reportbuyer.com/product/4807905/ MARKET INSIGHTS The ... of product, technology, application, and geography. The stem cell ...
(Date:3/30/2017)... The research team of The Hong Kong ... identification by adopting ground breaking 3D fingerprint minutiae recovery and matching ... and accuracy for use in identification, crime investigation, immigration control, security ... ... A research team led by ...
(Date:3/27/2017)... , March 27, 2017  Catholic Health ... and Management Systems Society (HIMSS) Analytics for achieving ... Adoption Model sm . In addition, CHS previously ... U.S. hospitals using an electronic medical record (EMR). ... its high level of EMR usage in an ...
Breaking Biology News(10 mins):
(Date:10/10/2017)... ... October 10, 2017 , ... San Diego-based team building and ... rebranding initiative announced today. The bold new look is part of a transformation ... moves into a significant growth period. , It will also expand its service offering ...
(Date:10/10/2017)... ... October 10, 2017 , ... For the ... won a US2020 STEM Mentoring Award. Representatives of the FirstHand program travelled to ... Experience from US2020. , US2020’s mission is to change the trajectory of STEM ...
(Date:10/10/2017)... Parks Associates announced today that Tom Kerber , Director ... , October 11 in Scottsdale, Arizona . Kerber will ... safety and security products impact the competitive landscape. ... Parks Associates: Smart Home Devices: Main Purchase Driver ... "The residential security market has experienced continued growth, and the introduction of ...
(Date:10/10/2017)... BARBARA, CALIFORNIA (PRWEB) , ... October 10, 2017 ... ... management, technological innovation and business process optimization firm for the life sciences and ... BoxWorks conference in San Francisco. , The presentation, “Automating GxP Validation ...
Breaking Biology Technology: