Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Testing the Fitness of Biological Clocks

25.08.2004


A traveler experiences jet lag when his or her internal clock becomes out-of-synch with the environment. Seasonal Affective Disorder, some types of depression, sleep disorders and problems adjusting to changes in work cycles all can occur when an individual’s biological clocks act up. Recent studies have even found links between these molecular time-pieces and cancer.



Microscopic pacemakers—also known as circadian clocks—are found in everything from pond scum to human beings and appear to help organize a dizzying array of biochemical processes. Despite the important role that they play, scientists are just beginning to understand the benefits that these internal pacemakers provide when they work and the problems they cause when they malfunction.

A study performed by researchers at Vanderbilt University and published in the Aug. 24 issue of the journal Current Biology sheds new light on this issue. Using blue-green algae—the simplest organism known to possess these mechanisms—the researchers report that the benefits of biological clocks are directly linked to environments with regular day/night cycle and totally disappear in conditions of constant illumination.


“Circadian clocks are so widespread that we think they must enhance the fitness of organisms by improving their ability to adapt to environmental influences, specifically daily changes in light, temperature and humidity,” says Carl H. Johnson, professor of biological sciences and Kennedy Center investigator who directed the study. “Some people have even suggested that, once invented, these clocks are such a powerful organizational tool that their benefits go beyond responding to external cycles. However, there have been practically no rigorous tests of either proposition.”

To test these ideas directly, Johnson’s research team used genetic engineering techniques to completely disrupt the biological clocks in one group of algae and to damp the frequency of the clocks in a second group. The researchers were careful to employ “point” mutations in the clock genes that didn’t stunt the growth of the microscopic plants.

They then mixed the algae with disrupted clocks with algae with normally functioning clocks. When the mixture was placed in an environment with a 24-hour day/night cycle, the normal algae grew dramatically faster than those that lacked functional internal timers. The normal algae also outperformed the algae with the damped clocks, but by a smaller margin.

The result was presaged by a series of experiments that Johnson conducted in 1998 with Susan S. Golden from Texas A&M University and Takao Kondo from Nagoya University. In the previous experiments, the researchers created two new algae strains with clocks of 22 hours and 30 hours. (The frequency of the biological clocks in normal blue-green algae is 25 hours.) They created mixed colonies by combining the strains in pairs: wild type and 22 hour; wild type and 30 hour; 22 hour and 30 hour. Then they put these mixed cultures into incubators with three different light-dark cycles—22 hours, 24 hours and 30 hours—and monitored them for about a month.

When they pulled the cultures out, the researchers found that the strain whose internal clock most closely matched the light-dark cycle invariably outgrew the competing strain. In fact, they found that the selective advantage of having the correctly tuned biological clock was surprisingly strong: The strains with matching frequencies grew 20 to 30 percent faster than the out-of-synch strains.

The second part of the current experiment was designed to test whether the biological clocks also provide an intrinsic advantage, a hypothesis advanced by the late Colin Pittendrigh of Stanford. He suggested that circadian clocks might be beneficial even in an unchanging environment. There was some indirect support for this proposition. In one experiment, for example, populations of the fruit fly, Drosophila melanogaster, were raised in constant illumination for hundreds of generations. Nevertheless, their biological clocks continued to function, suggesting that they continue to have adaptive value.

When the algae strains were placed in a chamber with constant light, however, the researchers were surprised to discover that the shoe was on the other foot: The algae with the disrupted internal clock divided and grew at a slightly faster rate than their clockwatching cousins, both those with natural biological clocks and those whose clocks were damped.

“This was the most surprising result of our study,” says Johnson. “Under constant conditions, the circadian clock system is of no benefit and, in fact, might even be bad for the algae.”

The scientist doesn’t know for certain why this happens, but he has some ideas. The microscopic plants use their biological clocks to turn their photosynthesis system on and off. In a normal 14-hour day/night cycle, this allows the microscopic plant to maximize the amount of chemical energy it can extract during daylight.

“In constant illumination, however, the biological clocks may keep shutting down photosynthesis in expectation of the darkness that never comes,” says Johnson.
Co-authors on the study are post-doctoral fellows Mark A. Woelfle and Yan Ouyang and graduate student Kittiporn Phanvijhitsiri. The research was supported by the National Institutes of Health.

| newswise
Further information:
http://www.vanderbilt.edu
http://www.exploration.vanderbilt.edu

More articles from Life Sciences:

nachricht Multi-institutional collaboration uncovers how molecular machines assemble
02.12.2016 | Salk Institute

nachricht Fertilized egg cells trigger and monitor loss of sperm’s epigenetic memory
02.12.2016 | IMBA - Institut für Molekulare Biotechnologie der Österreichischen Akademie der Wissenschaften GmbH

All articles from Life Sciences >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: Novel silicon etching technique crafts 3-D gradient refractive index micro-optics

A multi-institutional research collaboration has created a novel approach for fabricating three-dimensional micro-optics through the shape-defined formation of porous silicon (PSi), with broad impacts in integrated optoelectronics, imaging, and photovoltaics.

Working with colleagues at Stanford and The Dow Chemical Company, researchers at the University of Illinois at Urbana-Champaign fabricated 3-D birefringent...

Im Focus: Quantum Particles Form Droplets

In experiments with magnetic atoms conducted at extremely low temperatures, scientists have demonstrated a unique phase of matter: The atoms form a new type of quantum liquid or quantum droplet state. These so called quantum droplets may preserve their form in absence of external confinement because of quantum effects. The joint team of experimental physicists from Innsbruck and theoretical physicists from Hannover report on their findings in the journal Physical Review X.

“Our Quantum droplets are in the gas phase but they still drop like a rock,” explains experimental physicist Francesca Ferlaino when talking about the...

Im Focus: MADMAX: Max Planck Institute for Physics takes up axion research

The Max Planck Institute for Physics (MPP) is opening up a new research field. A workshop from November 21 - 22, 2016 will mark the start of activities for an innovative axion experiment. Axions are still only purely hypothetical particles. Their detection could solve two fundamental problems in particle physics: What dark matter consists of and why it has not yet been possible to directly observe a CP violation for the strong interaction.

The “MADMAX” project is the MPP’s commitment to axion research. Axions are so far only a theoretical prediction and are difficult to detect: on the one hand,...

Im Focus: Molecules change shape when wet

Broadband rotational spectroscopy unravels structural reshaping of isolated molecules in the gas phase to accommodate water

In two recent publications in the Journal of Chemical Physics and in the Journal of Physical Chemistry Letters, researchers around Melanie Schnell from the Max...

Im Focus: Fraunhofer ISE Develops Highly Compact, High Frequency DC/DC Converter for Aviation

The efficiency of power electronic systems is not solely dependent on electrical efficiency but also on weight, for example, in mobile systems. When the weight of relevant components and devices in airplanes, for instance, is reduced, fuel savings can be achieved and correspondingly greenhouse gas emissions decreased. New materials and components based on gallium nitride (GaN) can help to reduce weight and increase the efficiency. With these new materials, power electronic switches can be operated at higher switching frequency, resulting in higher power density and lower material costs.

Researchers at the Fraunhofer Institute for Solar Energy Systems ISE together with partners have investigated how these materials can be used to make power...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

ICTM Conference 2017: Production technology for turbomachine manufacturing of the future

16.11.2016 | Event News

Innovation Day Laser Technology – Laser Additive Manufacturing

01.11.2016 | Event News

#IC2S2: When Social Science meets Computer Science - GESIS will host the IC2S2 conference 2017

14.10.2016 | Event News

 
Latest News

UTSA study describes new minimally invasive device to treat cancer and other illnesses

02.12.2016 | Medical Engineering

Plasma-zapping process could yield trans fat-free soybean oil product

02.12.2016 | Agricultural and Forestry Science

What do Netflix, Google and planetary systems have in common?

02.12.2016 | Physics and Astronomy

VideoLinks
B2B-VideoLinks
More VideoLinks >>>