Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Rice study examines how bacteria acquire immunity

16.09.2010
First theoretical description of bacterial system to silence viral genes

In a new study this week, Rice University scientists bring the latest tools of computational biology to bear in examining how the processes of natural selection and evolution influence the way bacteria acquire immunity from disease.

The study is available online from Physical Review Letters. It builds upon one of the major discoveries made possible by molecular genetics in the past decade -- the revelation that bacteria and similar single-celled organisms have an acquired immune system.

"From a purely scientific perspective, this research is teaching us things we couldn't have imagined just a few years ago, but there's an applied interest in this work as well," said Michael Deem, the John W. Cox Professor in Biochemical and Genetic Engineering and professor of physics and astronomy at Rice. "It is believed, for instance, that the bacterial immune system uses a process akin to RNA interference to silence the disease genes it recognizes, and biotechnology companies may find it useful to develop this as a tool for silencing particular genes."

The new study by Deem and graduate student Jiankui He focused on a portion of the bacterial genome called the "CRISPR," which stands for "clustered regularly interspaced short palindromic repeats." The CRISPR contain two types of DNA sequences. One type -- short, repeating patterns that first attracted scientific interest -- is what led to the CRISPR name. But scientists more recently learned that the second type -- originally thought of as DNA "spacers" between the repeats -- is what the organism uses to recognize disease.

"Bacteria get attacked by viruses called phages, and the CRISPR contain genetic sequences from phages," Deem said. "The CRISPR system is both inheritable and programmable, meaning that some sequences may be there when the organism is first created, and new ones may also be added when new phages attack the organism during its life cycle."

The repeating sequences appear to be a kind of bookend or flag that the organism uses to determine where a snippet from a phage begins and ends. The CRISPR will often have between 30 and 50 of these snippets of phage sequences. Previous studies have found that once a bacteria has a phage sequence in its CRISPR, it has the ability to degrade any DNA or RNA that match that sequence -- meaning it can fend off attacks from any phages that have genes matching those in its CRISPR.

"What we wanted to explore was how the history of a bacterium's exposure to phages influences what's in the CRISPR," Deem said. "In other words, how is an organism's previous exposure to viruses reflected in its own genome?"

From earlier published studies, Deem and He knew that phage sequences were added to the CRISPR sequentially. So, in a CRISPR system containing 30 snippets, the newest one would be in position one, at the front of the line. In another study in 2007, researchers examining the CRISPR of whole populations of bacteria noticed some statistical irregularities. They found that the likelihood of two different organisms having the same snippet in their CRISPR increased exponentially as they progressed away from position one. So, in the organism with 30 snippets, the phage gene in position 30 was the most likely to be conserved time and again across all the bacteria in the population.

To use the power of computers to examine why this happens, Deem and He needed a mathematical description of what was happening over time to both the bacterial and phage populations. The equations they created reflect the way the bacterial and phage populations interact via the CRISPR.

"Each population is trying to expand, and selective pressure is constantly being applied on both sides," Deem said. "You can see how this plays out in the CRISPR over time. There's a diverse assortment of genes in the first spacer, but the second spacer has been in there longer, so there's been more selective pressure applied to that spacer. Because bacteria that contain the dominant viral strain in their CRISPR are more likely to survive than those that don't, they tend to squeeze out their neighbors that are more vulnerable. At position N, the farthest way from position one, selection has been at work the longest, so the genes we find there were the most common and the ones that tended to afford the most overall protection to the organism."

In addition to interest from biotechnology firms, Deem said the workings of the CRISPR are of interest to drugmakers who are investigating new types of antibiotics.

The research was supported by the Defense Advanced Research Projects Agency.

Jade Boyd | EurekAlert!
Further information:
http://www.rice.edu

Further reports about: CRISPR DNA DNA sequence RNA immune system molecular genetic single-celled organism

More articles from Studies and Analyses:

nachricht Antarctic Ice Sheet mass loss has increased
14.06.2018 | Technische Universität Dresden

nachricht WAKE-UP provides new treatment option for stroke patients | International study led by UKE
17.05.2018 | Universitätsklinikum Hamburg-Eppendorf

All articles from Studies and Analyses >>>

The most recent press releases about innovation >>>

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

Im Focus: Temperature-controlled fiber-optic light source with liquid core

In a recent publication in the renowned journal Optica, scientists of Leibniz-Institute of Photonic Technology (Leibniz IPHT) in Jena showed that they can accurately control the optical properties of liquid-core fiber lasers and therefore their spectral band width by temperature and pressure tuning.

Already last year, the researchers provided experimental proof of a new dynamic of hybrid solitons– temporally and spectrally stationary light waves resulting...

Im Focus: Overdosing on Calcium

Nano crystals impact stem cell fate during bone formation

Scientists from the University of Freiburg and the University of Basel identified a master regulator for bone regeneration. Prasad Shastri, Professor of...

Im Focus: AchemAsia 2019 will take place in Shanghai

Moving into its fourth decade, AchemAsia is setting out for new horizons: The International Expo and Innovation Forum for Sustainable Chemical Production will take place from 21-23 May 2019 in Shanghai, China. With an updated event profile, the eleventh edition focusses on topics that are especially relevant for the Chinese process industry, putting a strong emphasis on sustainability and innovation.

Founded in 1989 as a spin-off of ACHEMA to cater to the needs of China’s then developing industry, AchemAsia has since grown into a platform where the latest...

Im Focus: First real-time test of Li-Fi utilization for the industrial Internet of Things

The BMBF-funded OWICELLS project was successfully completed with a final presentation at the BMW plant in Munich. The presentation demonstrated a Li-Fi communication with a mobile robot, while the robot carried out usual production processes (welding, moving and testing parts) in a 5x5m² production cell. The robust, optical wireless transmission is based on spatial diversity; in other words, data is sent and received simultaneously by several LEDs and several photodiodes. The system can transmit data at more than 100 Mbit/s and five milliseconds latency.

Modern production technologies in the automobile industry must become more flexible in order to fulfil individual customer requirements.

Im Focus: Sharp images with flexible fibers

An international team of scientists has discovered a new way to transfer image information through multimodal fibers with almost no distortion - even if the fiber is bent. The results of the study, to which scientist from the Leibniz-Institute of Photonic Technology Jena (Leibniz IPHT) contributed, were published on 6thJune in the highly-cited journal Physical Review Letters.

Endoscopes allow doctors to see into a patient’s body like through a keyhole. Typically, the images are transmitted via a bundle of several hundreds of optical...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

VideoLinks
Industry & Economy
Event News

Munich conference on asteroid detection, tracking and defense

13.06.2018 | Event News

2nd International Baltic Earth Conference in Denmark: “The Baltic Sea region in Transition”

08.06.2018 | Event News

ISEKI_Food 2018: Conference with Holistic View of Food Production

05.06.2018 | Event News

 
Latest News

Creating a new composite fuel for new-generation fast reactors

20.06.2018 | Materials Sciences

Game-changing finding pushes 3D-printing to the molecular limit

20.06.2018 | Materials Sciences

Could this material enable autonomous vehicles to come to market sooner?

20.06.2018 | Materials Sciences

VideoLinks
Science & Research
Overview of more VideoLinks >>>