Even bacteria have a kind of “immune system” they use to defend themselves against unwanted intruders – in their case, viruses. Scientists at the Helmholtz Center for Infection Research (HZI) in Braunschweig, Germany, were now able to show that this defense system is much more diverse than previously thought and that it comes in multiple versions. Their goal is to use the various newly discovered versions of the CRISPR-Cas gene for the targeted manipulation of genetic information, particularly for medical purposes.
Streptococcus pyogenes, shown here while entering a cell, is one of the germs whose CRISPR-Cas system the scientists from Braunschweig have studied.
© HZI / Rohde
The human immune system’s main function is to protect us against invading bacteria, viruses, and other pathogens. To perform its job, the system has evolved into a highly complex ensemble of cells, messengers, and antibody molecules that is capable of recognizing different pathogens, defending us against them, and storing information about them.
Even the bacteria themselves are threatened by pathogens: Certain viruses, the bacteriophages (literally, “bacteria eaters”), have become specialized to invade bacterial cells and proliferate inside of them. In order to get rid of these unwanted guests, many species of bacteria make use of an arsenal of molecules that works according to similar principles as an immune system does.
The Cas enzyme recognizes DNA molecules that contain non-self genetic information, e.g. from bacteriophages, and cleaves them at specific sites. In order to recognize these molecules, a molecular copy of specific, characteristic sections of the foreign DNA is required. This copy, a kind of “molecular profile” of bacteriophage DNA and other foreign genetic material, exists as RNA, an important cellular building block, which is used, among other things, as a temporary storage site of genetic information.
The template for this profile is stored in the bacterium’s own genes, specifically in those regions scientists call CRISPR (which stands for “clustered regularly interspaced small palindromic repeats” or, more simply put, the “regular arrangement of small, symmetric repeats” in the sequence of the DNA building blocks).Together, the enzyme and the profile RNA constitute the CRISPR-Cas system.
“We were able to identify new CRISPR-Cas genes in a number of bacterial species,” says Charpentier, an HZI researcher who also teaches at Hannover Medical School (MHH). Among these species are much-feared germs like Streptococcus pyogenes and the meningitis pathogen, Neisseria meningitidis. “We have identified a number of these genes with the help of computers by examining known DNA sequences of the bacteria in question.” Charpentier’s conclusion: “The CRISPR system is not only widespread among bacteria, it also exists as an incredible range of different versions.”
Knowing about these different versions is not only of academic interest but can also be tremendously useful for gene technology: ”The CRISPR-Cas system is capable of cleaving DNA at very specific sites,” explains Charpentier. “The Cas enzyme can already be modified in such a way that it becomes active not only in bacteria but also in animal and human cell cultures.” If this kind of enzyme is specifically equipped with new RNA “profiles,” it cleaves the cell’s genome at precisely defined sites. “If you then use specific cellular repair mechanisms to mend the DNA strands and connect their loose ends, you can then specifically introduce new sections of genes into cellular DNA.”This opens considerable options for new forms of therapy. “I am certain that the CRISPR-Cas technology has tremendous potential,” says Charpentier. “Especially for medical applications like gene therapy.”
Dr. Jan Grabowski | Helmholtz-Zentrum
Single-stranded DNA and RNA origami go live
15.12.2017 | Wyss Institute for Biologically Inspired Engineering at Harvard
New antbird species discovered in Peru by LSU ornithologists
15.12.2017 | Louisiana State University
DNA molecules that follow specific instructions could offer more precise molecular control of synthetic chemical systems, a discovery that opens the door for engineers to create molecular machines with new and complex behaviors.
Researchers have created chemical amplifiers and a chemical oscillator using a systematic method that has the potential to embed sophisticated circuit...
MPQ scientists achieve long storage times for photonic quantum bits which break the lower bound for direct teleportation in a global quantum network.
Concerning the development of quantum memories for the realization of global quantum networks, scientists of the Quantum Dynamics Division led by Professor...
Researchers have developed a water cloaking concept based on electromagnetic forces that could eliminate an object's wake, greatly reducing its drag while...
Tiny pores at a cell's entryway act as miniature bouncers, letting in some electrically charged atoms--ions--but blocking others. Operating as exquisitely sensitive filters, these "ion channels" play a critical role in biological functions such as muscle contraction and the firing of brain cells.
To rapidly transport the right ions through the cell membrane, the tiny channels rely on a complex interplay between the ions and surrounding molecules,...
The miniaturization of the current technology of storage media is hindered by fundamental limits of quantum mechanics. A new approach consists in using so-called spin-crossover molecules as the smallest possible storage unit. Similar to normal hard drives, these special molecules can save information via their magnetic state. A research team from Kiel University has now managed to successfully place a new class of spin-crossover molecules onto a surface and to improve the molecule’s storage capacity. The storage density of conventional hard drives could therefore theoretically be increased by more than one hundred fold. The study has been published in the scientific journal Nano Letters.
Over the past few years, the building blocks of storage media have gotten ever smaller. But further miniaturization of the current technology is hindered by...
11.12.2017 | Event News
08.12.2017 | Event News
07.12.2017 | Event News
15.12.2017 | Power and Electrical Engineering
15.12.2017 | Materials Sciences
15.12.2017 | Life Sciences