ETH Zurich biologists, led by Professors Martin Ackermann and Wolf-Dietrich Hardt, in collaboration with Michael Doebeli of the University of British Colombia in Vancouver (CN), have been able to describe how random molecular processes during cell division allow some cells to engage in a self-destructive act to generate a greater common good, thereby improving the situation of the surviving siblings.
The biologists investigated this unusual biological concept using the pathogenic salmo-nella bacteria as an example. Diseases caused by salmonellae are very unpleasant and even life-threatening. When contaminated food is consumed – for example, egg-based foods or chicken and meat – salmonella bacteria enter the gastro-intestinal tract where it triggers infection. Vomiting and diarrhoea can last for days.
Normally, salmonellae grow poorly in the intestine because they are not competitive with other bacteria of the gut. However, this dynamic changes if salmonellae induce an inflammatory response, namely diarrhoea, which suppresses the other bacteria. The inflammation is triggered by salmonellae penetrating into the intestinal tissues. Once inside, salmonellae is killed by the immune system. This in turn creates a conflict: salmonellae are either suppressed by the other bacteria in the gut, or die while trying to eliminate these competitors.
As Ackermann, Hardt and Doebeli report, salmonellae have found a surprising solution to this conflict. Inside the gut, the samonella bacteria forms two groups that engage in job-sharing. A first group invades the tissue, triggers an inflammation, then dies. A second group waits inside the gut until the inactivation of the normal intestinal flora gives them an opportunity to strike.This second group then multiplies unhindered.
Random processes and self-sacrifice
What determines whether an individual salmonella bacterium cell self-sacrifices, or whether it will wait and benefit from the sacrifice of others? The two groups are clones of the same genotype, so genetic differences do not play a role. Rather, the difference between the two groups is a result of random molecular processes during cell division. Cellular components are randomly distributed between the two daughter cells with each cell receiving a different amount. The resulting imbalance can be amplified and lead to different properties of the clonal siblings.
In recent years it has been recognized that such random processes in a cell can have a large influence on individual cells. The work by the ETH Zurich researchers reveals a new biological explanation for this phenomenon. The two salmonella phenotypes share their work, with the result being that they achieve what a single phenotype on its own would not be capable of doing. This scenario is fundamentally different from the usual explanations and presupposes that individual phenotypes interact and have an effect on one another. The self-sacrifice of phenotypes may be quite common among pathogenic bacteria, for example, among the pathogens causing diarrhoea after antibiotic treatment (clostridia) or pneumonia (streptococci).
Professor Ackermann says that “Random processes could promote job-sharing in many different types of organisms.” Many bacteria manufacture substances which are toxic to their hosts but which are only released into the host environment if the bacteria sacrifice themselves - if this is the sole method to get the toxin out of the cell. This is why every cell makes a decision: toxin and death or no toxin.
He stresses that it would not have been possible to study this theory so thoroughly with-out the collaboration that took place among the three specialist groups: Professor Hardt’s group specialises in salmonella infections; Professor Doebeli is a mathematician and theoretical biologist; and Professor Ackermann’s group focuses on phenotypic noise.
Roman Klingler | alfa
Multi-year study finds 'hotspots' of ammonia over world's major agricultural areas
17.03.2017 | University of Maryland
Diabetes Drug May Improve Bone Fat-induced Defects of Fracture Healing
17.03.2017 | Deutsches Institut für Ernährungsforschung Potsdam-Rehbrücke
Astronomers from Bonn and Tautenburg in Thuringia (Germany) used the 100-m radio telescope at Effelsberg to observe several galaxy clusters. At the edges of these large accumulations of dark matter, stellar systems (galaxies), hot gas, and charged particles, they found magnetic fields that are exceptionally ordered over distances of many million light years. This makes them the most extended magnetic fields in the universe known so far.
The results will be published on March 22 in the journal „Astronomy & Astrophysics“.
Galaxy clusters are the largest gravitationally bound structures in the universe. With a typical extent of about 10 million light years, i.e. 100 times the...
Researchers at the Goethe University Frankfurt, together with partners from the University of Tübingen in Germany and Queen Mary University as well as Francis Crick Institute from London (UK) have developed a novel technology to decipher the secret ubiquitin code.
Ubiquitin is a small protein that can be linked to other cellular proteins, thereby controlling and modulating their functions. The attachment occurs in many...
In the eternal search for next generation high-efficiency solar cells and LEDs, scientists at Los Alamos National Laboratory and their partners are creating...
Silicon nanosheets are thin, two-dimensional layers with exceptional optoelectronic properties very similar to those of graphene. Albeit, the nanosheets are less stable. Now researchers at the Technical University of Munich (TUM) have, for the first time ever, produced a composite material combining silicon nanosheets and a polymer that is both UV-resistant and easy to process. This brings the scientists a significant step closer to industrial applications like flexible displays and photosensors.
Silicon nanosheets are thin, two-dimensional layers with exceptional optoelectronic properties very similar to those of graphene. Albeit, the nanosheets are...
Enzymes behave differently in a test tube compared with the molecular scrum of a living cell. Chemists from the University of Basel have now been able to simulate these confined natural conditions in artificial vesicles for the first time. As reported in the academic journal Small, the results are offering better insight into the development of nanoreactors and artificial organelles.
Enzymes behave differently in a test tube compared with the molecular scrum of a living cell. Chemists from the University of Basel have now been able to...
20.03.2017 | Event News
14.03.2017 | Event News
07.03.2017 | Event News
23.03.2017 | Life Sciences
23.03.2017 | Power and Electrical Engineering
23.03.2017 | Earth Sciences