Featured Research

from universities, journals, and other organizations

Pulsating response to stress in bacteria discovered

Date:
November 4, 2011
Source:
California Institute of Technology
Summary:
Turning on the heater is a reasonable response to a cold environment: switch to a toastier state until it warms up outside. Biologists have long thought cells would respond to their environment in a similar way. But now researchers are finding that cells can respond using a pulsating mechanism. The principles behind this process are surprisingly simple and could drive other cellular processes, revealing more about how the cells -- and ultimately life -- work.

By attaching fluorescent proteins to the genetic circuit responsible for B. subtilis's stress response, the researchers can observe the cells' pulses as green flashes. Watch a video of the flashing cells as they multiply over the course of more than 12 hours at: http://www.youtube.com/watch?v=qWkLS-u982A
Credit: Caltech/Elowitz Lab

If the changing seasons are making it chilly inside your house, you might just turn the heater on. That's a reasonable response to a cold environment: switching to a toastier and more comfortable state until it warms up outside. And so it's no surprise that biologists have long thought cells would respond to their environment in a similar way.

Related Articles


But now researchers at the California Institute of Technology (Caltech) are finding that cells can respond using a new kind of pulsating mechanism, instead of just shifting from one steady state to another and staying there. The principles behind this process are surprisingly simple, the researchers say, and could drive other cellular processes, revealing more about how the cells -- and ultimately life -- work.

In their experiment, the researchers studied how a bacterial species called B. subtilis responds to a stressful environment -- for example, one without food. In such conditions, the single-celled organism activates a large set of genes that help it deal with hardship, by aiding cell repair for instance. Previously, biologists had thought the bacteria would handle stress by turning on the relevant genes and simply leaving them on until the stress goes away.

Instead, the researchers found that B. subtilis continuously flips these genes on and off. When faced with more stress, it increases the frequency of these pulses. The pulsating action is like switching your heater on full blast for a brief period every few minutes, and turning it on and off more frequently if you want the house to be warmer.

"It's a very different view of how a cell can respond to a particular stress," says James Locke, a postdoctoral scholar at Caltech. Locke and graduate student Jonathan Young are the lead authors on a paper describing this work, which was published in the Oct. 21 issue of Science.

To make their finding, the researchers introduced a chemical to B. subtilis that inhibits the production of ATP, the energy-carrying molecules of cells. The team found that the stress induced by this chemical triggers interactions within a set of genes -- collectively called a genetic circuit. This circuit, which contains a set of positive and negative feedback loops, generates sustained pulses of activity in a key regulatory protein called σB ("sigma B"). The researchers attached fluorescent proteins to the circuit, causing the cells to glow green when σB was activated. By making movies of the flashing cells, the team could then study the dynamics of the circuit.

The key to this pulsating mechanism is the variability inherent in how proteins are made, the researchers say. The number of copies of any specific protein in a given cell fluctuates over time. The bacterial gene circuit amplifies these molecular fluctuations, also called noise, to generate discrete pulses of σB activation. The stress also activates another key protein that modulates the pulse frequencies.

By turning a steady input (the stress) into an oscillating output (the activation of σB) the genetic circuit is analogous to an electrical inverter, a device that converts direct current (DC) into alternating current (AC), explains Michael Elowitz, professor of biology and bioengineering at Caltech, Howard Hughes Medical Institute investigator, and coauthor of the paper. "You might think you need some kind of elaborate circuitry to implement that, but the cell can do it with just a few proteins, and by taking advantage of noise."

This work provides a blueprint for how relatively simple genetic circuits can generate complex and dynamic behaviors in individual cells, the researchers say. "We're excited to think that similar mechanisms may occur in other cellular processes," Locke says. "It'd be interesting in the future to see which aspects of this circuit architecture also appear in more complex systems, such as mammalian cells."

"With this work and recent work in other systems, we're starting to get a glimpse of just how dynamic cellular control systems really are," Elowitz adds. "That's something that was very difficult to see in the past."

The other authors of the Science paper, "Stochastic pulse regulation in bacterial stress response," are research technicians Michelle Fontes and Maria Jesus Hernandez Jimenez. The research was funded by the National Institutes of Health, the National Science Foundation, the Packard Foundation, the International Human Frontier Science Organization, and the European Molecular Biology Organization.


Story Source:

The above story is based on materials provided by California Institute of Technology. The original article was written by Marcus Woo. Note: Materials may be edited for content and length.


Journal Reference:

  1. J. C. W. Locke, J. W. Young, M. Fontes, M. J. H. Jimenez, M. B. Elowitz. Stochastic Pulse Regulation in Bacterial Stress Response. Science, 2011; 334 (6054): 366 DOI: 10.1126/science.1208144

Cite This Page:

California Institute of Technology. "Pulsating response to stress in bacteria discovered." ScienceDaily. ScienceDaily, 4 November 2011. <www.sciencedaily.com/releases/2011/11/111103120607.htm>.
California Institute of Technology. (2011, November 4). Pulsating response to stress in bacteria discovered. ScienceDaily. Retrieved January 27, 2015 from www.sciencedaily.com/releases/2011/11/111103120607.htm
California Institute of Technology. "Pulsating response to stress in bacteria discovered." ScienceDaily. www.sciencedaily.com/releases/2011/11/111103120607.htm (accessed January 27, 2015).

Share This


More From ScienceDaily



More Plants & Animals News

Tuesday, January 27, 2015

Featured Research

from universities, journals, and other organizations


Featured Videos

from AP, Reuters, AFP, and other news services

How To: Mixed Green Salad Topped With Camembert Cheese

How To: Mixed Green Salad Topped With Camembert Cheese

Rumble (Jan. 26, 2015) Learn how to make a mixed green salad topped with a pan-seared camembert cheese in only a minute! Music: Courtesy of Audio Network. Video provided by Rumble
Powered by NewsLook.com
Water Fleas Prepare for Space Voyage

Water Fleas Prepare for Space Voyage

Reuters - Innovations Video Online (Jan. 26, 2015) Scientists are preparing a group of water fleas for a unique voyage into space. The aquatic crustaceans, known as Daphnia, can be used as a miniature model for biomedical research, and their reproductive and swimming behaviour will be tested for signs of stress while on board the International Space Station. Jim Drury went to meet the team. Video provided by Reuters
Powered by NewsLook.com
Husky Puppy Plays With Ferret

Husky Puppy Plays With Ferret

Rumble (Jan. 26, 2015) It looks like this 2-month-old Husky puppy and the family ferret are going to be the best of friends. Look at how much fun they&apos;re having together! Credit to &apos;Vira&apos;. Video provided by Rumble
Powered by NewsLook.com
Scientists Model Flying, Walking Drone After Vampire Bats

Scientists Model Flying, Walking Drone After Vampire Bats

Buzz60 (Jan. 26, 2015) Swiss scientists build a new drone that can both fly and walk, modeling it after the movements of common vampire bats. Jen Markham (@jenmarkham) has the story. Video provided by Buzz60
Powered by NewsLook.com

Search ScienceDaily

Number of stories in archives: 140,361

Find with keyword(s):
Enter a keyword or phrase to search ScienceDaily for related topics and research stories.

Save/Print:
Share:

Breaking News:

Strange & Offbeat Stories


Plants & Animals

Earth & Climate

Fossils & Ruins

In Other News

... from NewsDaily.com

Science News

    Health News

    Environment News

    Technology News



    Save/Print:
    Share:

    Free Subscriptions


    Get the latest science news with ScienceDaily's free email newsletters, updated daily and weekly. Or view hourly updated newsfeeds in your RSS reader:

    Get Social & Mobile


    Keep up to date with the latest news from ScienceDaily via social networks and mobile apps:

    Have Feedback?


    Tell us what you think of ScienceDaily -- we welcome both positive and negative comments. Have any problems using the site? Questions?
    Mobile: iPhone Android Web
    Follow: Facebook Twitter Google+
    Subscribe: RSS Feeds Email Newsletters
    Latest Headlines Health & Medicine Mind & Brain Space & Time Matter & Energy Computers & Math Plants & Animals Earth & Climate Fossils & Ruins