Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:


Rice study decodes genetic circuitry for bacterial spore formation


Bacterial survival switch triggered by growth rate

A team led by Rice University bioengineering researchers has decoded the mechanism that some bacteria use to make life-or-death decisions during extremely tough times.

A mixed population of starving Bacillus subtilis cells includes both nonsporulating cells (dark blue) and cells that have begun spore formation by dividing asymmetrically into large (yellow) and small (pink) chambers.

Credit: M. Fujita/UH

Deciphering how bacteria respond to stress could yield new clues for combating food spoilage and for controlling food-borne pathogens. The new study was published in Molecular Systems Biology and sheds light on a long-standing debate about one of the field's fundamental questions: What causes stressed-out bacteria to make the drastic move to cease normal functions and form spores?

"What people in our field have long wondered is, How do spore-forming bacteria like Bacillus make this decision?" said study co-author Oleg Igoshin, associate professor of bioengineering at Rice and a senior investigator at Rice's Center for Theoretical Biological Physics (CTBP). "Is there a specific biochemical trigger that activates one of the network proteins or is sporulation more of a general physiological response?"

To form a hard-shelled spore, which can survive for years without food, the organism must pour its energy into sporulation. Becoming a spore too soon can lead to death by competition -- from neighbors that keep multiplying -- but delaying the decision can lead to death by starvation before the spore is complete.

"It's a high-stakes decision, which suggests that the decision mechanism has come about through intense evolutionary pressure," Igoshin said. "It's also possible that organisms have adopted this same mechanism to make other critical decisions."

B. subtilis is a common soil bacteria and a well-known survivor. It isn't harmful to humans and is even used as a probiotic in some traditional foods. It is so good at forming spores that it's the model organism of choice for biologists who study sporulation.

Almost a decade ago, Igoshin, a computational biologist, began studying the regulatory genes that B. subtilis uses to make sporulation decisions. He and members of his lab interpret the work of experimental collaborators and develop computer simulations to decipher the workings of the regulatory network, such as the switches, feedback loops and signal amplifiers, that B. subtilis uses to make its decision.

In 2012 Igoshin and graduate student Jatin Narula showed how the regulatory network employs a series of nested "feed-forward" loops to filter signal noise, and in 2015 they revealed the network's timing mechanism, a circuit that uses the organism's clock-like DNA replication cycle.

In the new study, which builds upon the 2015 work, Narula, Igoshin and collaborators used their computer model to show how a general physiological cue -- the slowdown of cellular growth -- can trigger B. subtilis' sporulation decisions. Igoshin said the sporulation network is very sensitive to the concentration of a key protein that the cell produces at an essentially constant rate. During starvation, when the cell's growth rate slows, the concentration of this protein builds up, and the bacteria are more likely to form spores. The theoretical work at Rice was experimentally tested in the lab of co-author Gürol Süel of the University of California at San Diego.

Experiments performed by two graduate students in Süel's lab, Anna Kuchina and Fang Zhang, confirmed the main model prediction: Only cells that slow down their growth beyond a threshold value proceed to sporulation. The experimental data indicated that the amount of sporulation network proteins -- but not the activity of the proteins -- was modulated by cell growth, a finding that contradicts the theory that there is a specific biochemical trigger for sporulation.

Igoshin said the finding has important implications for food safety and general microbiology.

"Sporulation by some of the close relatives of B. subtilis is a big hassle for the food-preservation industry because many of those spores can survive boiling temperatures," Igoshin said. "To kill those spores, you need to apply both heat and high pressure. So people have been looking for other methods to inhibit sporulation. If sporulation was triggered by a specific molecule, then perhaps a drug could be found to block that molecule, but our research suggests that sporulation is a general physiological response and that food safety engineers will need to look for other methods of control.

"Moreover, there is a good chance that this mechanism controls key decisions in other bacterial species," he said. "It ties to very basic bacterial physiology, and as a result, I think it may be universal."


Masaya Fujita of the University of Houston is also a co-author of the study. The research was supported by the National Science Foundation, the National Institutes of Health and the Howard Hughes Medical Institute.

The DOI of the Molecular Systems Biology paper is: 10.15252/msb.20156691

A copy of the paper is available at:

Related B. subtilis research from Rice:

Bacteria use DNA replication to time key decision -- July 9, 2015

Deciphering bacterial doomsday decisions -- Nov. 26, 2012

Stem cells: in search of a master controller -- May 7, 2010

Are sacrificial bacteria altruistic or just unlucky? -- April 16, 2008

This release can be found online at

Follow Rice News and Media Relations on Twitter @RiceUNews.

Located on a 300-acre forested campus in Houston, Rice University is consistently ranked among the nation's top 20 universities by U.S. News & World Report. Rice has highly respected schools of Architecture, Business, Continuing Studies, Engineering, Humanities, Music, Natural Sciences and Social Sciences and is home to the Baker Institute for Public Policy. With 3,910 undergraduates and 2,809 graduate students, Rice's undergraduate student-to-faculty ratio is 6-to-1. Its residential college system builds close-knit communities and lifelong friendships, just one reason why Rice is ranked No. 1 for best quality of life and for lots of race/class interaction by the Princeton Review. Rice is also rated as a best value among private universities by Kiplinger's Personal Finance. To read "What they're saying about Rice," go to

Media Contact

David Ruth


David Ruth | EurekAlert!

More articles from Life Sciences:

nachricht Don't Give the Slightest Chance to Toxic Elements in Medicinal Products
23.03.2018 | Physikalisch-Technische Bundesanstalt (PTB)

nachricht North and South Cooperation to Combat Tuberculosis
22.03.2018 | Universität Zürich

All articles from Life Sciences >>>

The most recent press releases about innovation >>>

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

Im Focus: Space observation with radar to secure Germany's space infrastructure

Satellites in near-Earth orbit are at risk due to the steady increase in space debris. But their mission in the areas of telecommunications, navigation or weather forecasts is essential for society. Fraunhofer FHR therefore develops radar-based systems which allow the detection, tracking and cataloging of even the smallest particles of debris. Satellite operators who have access to our data are in a better position to plan evasive maneuvers and prevent destructive collisions. From April, 25-29 2018, Fraunhofer FHR and its partners will exhibit the complementary radar systems TIRA and GESTRA as well as the latest radar techniques for space observation across three stands at the ILA Berlin.

The "traffic situation" in space is very tense: the Earth is currently being orbited not only by countless satellites but also by a large volume of space...

Im Focus: Researchers Discover New Anti-Cancer Protein

An international team of researchers has discovered a new anti-cancer protein. The protein, called LHPP, prevents the uncontrolled proliferation of cancer cells in the liver. The researchers led by Prof. Michael N. Hall from the Biozentrum, University of Basel, report in “Nature” that LHPP can also serve as a biomarker for the diagnosis and prognosis of liver cancer.

The incidence of liver cancer, also known as hepatocellular carcinoma, is steadily increasing. In the last twenty years, the number of cases has almost doubled...

Im Focus: Researchers at Fraunhofer monitor re-entry of Chinese space station Tiangong-1

In just a few weeks from now, the Chinese space station Tiangong-1 will re-enter the Earth's atmosphere where it will to a large extent burn up. It is possible that some debris will reach the Earth's surface. Tiangong-1 is orbiting the Earth uncontrolled at a speed of approx. 29,000 km/h.Currently the prognosis relating to the time of impact currently lies within a window of several days. The scientists at Fraunhofer FHR have already been monitoring Tiangong-1 for a number of weeks with their TIRA system, one of the most powerful space observation radars in the world, with a view to supporting the German Space Situational Awareness Center and the ESA with their re-entry forecasts.

Following the loss of radio contact with Tiangong-1 in 2016 and due to the low orbital height, it is now inevitable that the Chinese space station will...

Im Focus: Alliance „OLED Licht Forum“ – Key partner for OLED lighting solutions

Fraunhofer Institute for Organic Electronics, Electron Beam and Plasma Technology FEP, provider of research and development services for OLED lighting solutions, announces the founding of the “OLED Licht Forum” and presents latest OLED design and lighting solutions during light+building, from March 18th – 23rd, 2018 in Frankfurt a.M./Germany, at booth no. F91 in Hall 4.0.

They are united in their passion for OLED (organic light emitting diodes) lighting with all of its unique facets and application possibilities. Thus experts in...

Im Focus: Mars' oceans formed early, possibly aided by massive volcanic eruptions

Oceans formed before Tharsis and evolved together, shaping climate history of Mars

A new scenario seeking to explain how Mars' putative oceans came and went over the last 4 billion years implies that the oceans formed several hundred million...

All Focus news of the innovation-report >>>



Industry & Economy
Event News

New solar solutions for sustainable buildings and cities

23.03.2018 | Event News

Virtual reality conference comes to Reutlingen

19.03.2018 | Event News

Ultrafast Wireless and Chip Design at the DATE Conference in Dresden

16.03.2018 | Event News

Latest News

Don't Give the Slightest Chance to Toxic Elements in Medicinal Products

23.03.2018 | Life Sciences

Sensitive grip

23.03.2018 | Materials Sciences

No compromises: Combining the benefits of 3D printing and casting

23.03.2018 | Process Engineering

Science & Research
Overview of more VideoLinks >>>