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 Deep-sea bacteria copy their neighbors' diet
19.11.2019 | Max-Planck-Institut für Marine Mikrobiologie

nachricht Structure of a mitochondrial ATP synthase
19.11.2019 | Science For Life Laboratory

All articles from Life Sciences >>>

The most recent press releases about innovation >>>

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

Im Focus: Atoms don't like jumping rope

Nanooptical traps are a promising building block for quantum technologies. Austrian and German scientists have now removed an important obstacle to their practical use. They were able to show that a special form of mechanical vibration heats trapped particles in a very short time and knocks them out of the trap.

By controlling individual atoms, quantum properties can be investigated and made usable for technological applications. For about ten years, physicists have...

Im Focus: Images from NJIT's big bear solar observatory peel away layers of a stellar mystery

An international team of scientists, including three researchers from New Jersey Institute of Technology (NJIT), has shed new light on one of the central mysteries of solar physics: how energy from the Sun is transferred to the star's upper atmosphere, heating it to 1 million degrees Fahrenheit and higher in some regions, temperatures that are vastly hotter than the Sun's surface.

With new images from NJIT's Big Bear Solar Observatory (BBSO), the researchers have revealed in groundbreaking, granular detail what appears to be a likely...

Im Focus: New opportunities in additive manufacturing presented

Fraunhofer IFAM Dresden demonstrates manufacturing of copper components

The Fraunhofer Institute for Manufacturing Technology and Advanced Materials IFAM in Dresden has succeeded in using Selective Electron Beam Melting (SEBM) to...

Im Focus: New Pitt research finds carbon nanotubes show a love/hate relationship with water

Carbon nanotubes (CNTs) are valuable for a wide variety of applications. Made of graphene sheets rolled into tubes 10,000 times smaller than a human hair, CNTs have an exceptional strength-to-mass ratio and excellent thermal and electrical properties. These features make them ideal for a range of applications, including supercapacitors, interconnects, adhesives, particle trapping and structural color.

New research reveals even more potential for CNTs: as a coating, they can both repel and hold water in place, a useful property for applications like printing,...

Im Focus: Magnets for the second dimension

If you've ever tried to put several really strong, small cube magnets right next to each other on a magnetic board, you'll know that you just can't do it. What happens is that the magnets always arrange themselves in a column sticking out vertically from the magnetic board. Moreover, it's almost impossible to join several rows of these magnets together to form a flat surface. That's because magnets are dipolar. Equal poles repel each other, with the north pole of one magnet always attaching itself to the south pole of another and vice versa. This explains why they form a column with all the magnets aligned the same way.

Now, scientists at ETH Zurich have managed to create magnetic building blocks in the shape of cubes that - for the first time ever - can be joined together to...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

VideoLinks
Industry & Economy
Event News

First International Conference on Agrophotovoltaics in August 2020

15.11.2019 | Event News

Laser Symposium on Electromobility in Aachen: trends for the mobility revolution

15.11.2019 | Event News

High entropy alloys for hot turbines and tireless metal-forming presses

05.11.2019 | Event News

 
Latest News

How LISA pathfinder detected dozens of 'comet crumbs'

19.11.2019 | Physics and Astronomy

Trash talk hurts, even when it comes from a robot

19.11.2019 | Social Sciences

The evolution and genomic basis of beetle diversity

19.11.2019 | Life Sciences

VideoLinks
Science & Research
Overview of more VideoLinks >>>