In order to get rid of unpleasant competitors, some bacteria use a sophisticated weapon – a nanosized speargun. Researchers at the University of Basel’s Biozentrum have now gained new insights into the construction, mode of action and recycling of this weapon. As they report in the journal “Nature Microbiology”, the speargun drills a hole into the neighboring cells in only a few thousandths of a second and injects a cocktail of toxins.
Millions of tiny microbes on leaves, stones or our skin jostle for space. And almost everywhere they have to compete for resources and nutrients. In the course of evolution, some bacteria have therefore developed a weapon to inject a toxic cocktail into competitors and rivals in their neighborhood, thus eliminating them. Among experts, this weapon resembling a speargun is also known as the type VI secretion system (T6SS).
Two years ago, Prof. Marek Basler was able to elucidate the atomic structure of the speargun in the “post-firing” state. In the current study, which was carried out in cooperation with various research groups and technology platforms at the Biozentrum, his team has now solved the structure of the “ready to fire” speargun. Based on these findings, the researchers have been able to model how this T6SS speargun works.
Structure of nanosized speargun changes during firing
The speargun is composed of various components, including a sheath and a spear with a sharp tip. The sheath consists of over 200 connected cogwheel-like protein rings that are assembled around the inner rigid spear. When T6SS fires, the sheath rapidly contracts and pushes the toxic spear out of the cell, which can then penetrate into neighboring cells where it releases deadly toxins. “So far, there have only been assumptions as to how the structure of the T6SS sheath changes during contraction,” says Basler. “Using cryo-electron microscopy available at C-CINA, we have now obtained an image of the spear and the extended sheath in atomic resolution.”
By comparing the structures of the extended and contracted states, the researchers were able to model how the T6SS works in detail. “During the sheath contraction, ring after ring turns and gets closer to the previous ring, while the ring diameter expands and thus releases the spear,” explains Basler. “This combination of sheath shrinking and turning results in drilling a hole into the target cells. Within less than two milliseconds, the T6SS sheath contracts to half of its length and at the same time the toxic spear spirals out like a screw. Therefore, the bacteria have an extremely powerful drill.”
Only contracted T6SS sheaths are disassembled
Furthermore, the researchers also addressed another question. After firing T6SS, bacteria re-use the individual components of the sheath to assemble a new speargun. “For a long time, it was not clear why only the contracted, but not the extended sheath is disassembled,” says Basler. “Now, we could see that a certain protein domain is exposed on the surface of the sheath during contraction and can be recognized by a specific protein responsible for dismantling the sheath. In the extended sheath state, this domain is hidden and the T6SS sheath is therefore protected from disassembly.”
The bacterial speargun will continue to be the subject of future research. “One of our projects is dedicated to the question of how the T6SS is embedded in the bacterial cell envelope. As the speargun is fired with such a high force, it must be firmly anchored, otherwise firing would not work properly or could be also fatal for the weapon-carrying bacteria themselves.”
Jing Wang, Maximilian Brackmann, Daniel Castaño-Díez, Mikhail Kudryashev, Kenneth N. Goldie, Timm Maier, Henning Stahlberg and Marek Basler
Cryo-EM structure of the extended type VI secretion system sheath-tube complex
Nature Microbiology (2017), doi: 10.1038/s41564-017-0020-7
Video: Prof. Marek Basler, Bacterial nanosized speargun
Prof. Dr. Marek Basler, University of Basel, Biozentrum, Tel. +41 61 207 21 10, email: firstname.lastname@example.org
Dr. Katrin Bühler, University of Basel, Biozentrum, Communications, Tel. +41 61 207 09 74, email: email@example.com
Dr. Katrin Bühler | Universität Basel
OHIO professor Hla develops robust molecular propeller for unidirectional rotations
22.08.2019 | Ohio University
In cystic fibrosis, lungs feed deadly bacteria
22.08.2019 | Columbia University Irving Medical Center
Theoretical physicists at Trinity College Dublin are among an international collaboration that has built the world's smallest engine - which, as a single calcium ion, is approximately ten billion times smaller than a car engine.
Work performed by Professor John Goold's QuSys group in Trinity's School of Physics describes the science behind this tiny motor.
Together with the University of Innsbruck, the ETH Zurich and Interactive Fully Electrical Vehicles SRL, Infineon Austria is researching specific questions on the commercial use of quantum computers. With new innovations in design and manufacturing, the partners from universities and industry want to develop affordable components for quantum computers.
Ion traps have proven to be a very successful technology for the control and manipulation of quantum particles. Today, they form the heart of the first...
Experimental progress towards engineering quantized gauge fields coupled to ultracold matter promises a versatile platform to tackle problems ranging from condensed-matter to high-energy physics
The interaction between fields and matter is a recurring theme throughout physics. Classical cases such as the trajectories of one celestial body moving in the...
Soft robots have a distinct advantage over their rigid forebears: they can adapt to complex environments, handle fragile objects and interact safely with humans. Made from silicone, rubber or other stretchable polymers, they are ideal for use in rehabilitation exoskeletons and robotic clothing. Soft bio-inspired robots could one day be deployed to explore remote or dangerous environments.
Most soft robots are actuated by rigid, noisy pumps that push fluids into the machines' moving parts. Because they are connected to these bulky pumps by tubes,...
Researchers at TU Graz are working together with European partners on new possibilities of measuring vehicle emissions.
Today, air pollution is one of the biggest challenges facing European cities. As part of the Horizon 2020 research project CARES (City Air Remote Emission...
16.08.2019 | Event News
14.08.2019 | Event News
12.08.2019 | Event News
22.08.2019 | Life Sciences
22.08.2019 | Physics and Astronomy
22.08.2019 | Physics and Astronomy