Microorganisms can better withstand the heavy metal uranium when glutathione is present, a molecule composed of three amino acids. Scientists from the German based Helmholtz-Zentrum Dresden-Rossendorf (HZDR) and the University of Bern in Switzerland have now proven this resilience by closely examining cell heat balance. They discovered that glutathione is an effective decontamination agent. The studies provide important insights into bioremediation of mining waste piles and other contaminated areas with the help of bacteria or plants.
Living cells are small power stations in which various chemical reactions take place, releasing tiny amounts of heat. Metabolism is stimulated when the cells are exposed to uranium, without, however, leading to increased growth.
This extra effort is detectable in the organisms as increased heat emission – signaling their fight against the toxin. The four-person team from Dresden and Bern (Dr. Muhammad H. Obeid, Dr. Jana Oertel, Prof. Marc Solioz, Prof. Karim Fahmy) established a highly sensitive method, known as microcalorimetry, with which this power can be measured – even if it lies only in the microwatt (a millionth of a watt) range.
Through their tests, the researchers furthermore determine the culture cell count and thus register how the cells divide and grow. Karim Fahmy summarizes the results: “We have found out that the metabolism with uranium becomes less efficient. The cells produce more heat but not more cells. They’re virtually running a temperature!”
The organisms clearly use their energy for defense mechanisms rather than for growth. A completely different picture emerges when glutathione is present. In this case, the cells continue to grow. “Glutathione lowers uranium’s chemical toxicity. The cells better withstand the contamination," says the biophysicist.
A bacterium from cheese production, Lactococcus lactis, was chosen for the studies. The researchers used a strain with an artificially introduced hereditary predisposition for glutathione production. The gene can be selectively switched on or off. This allows precise control of whether the cells produce glutathione or not. Karim Fahmy explains, “We thereby have a clean model and do not need to add the glutathione from the outside.” Disruptive factors are thus excluded.
These new insights on the protective effects of glutathione are important for innovative strategies in biological heavy metal decontamination in the environment. The process known as bioremediation attempts to harness plants or bacteria for the removal of toxins from contaminated sites. The organisms absorb the contaminants, which are removed from the site under controlled conditions through a subsequent “harvest”. The procedure also appears suitable for uranium decontamination. As is clear from the HZDR researchers’ findings, a preference should be given to organisms with their own glutathione biosynthesis.
Glutathione has already been discussed for quite a long time as a decontaminant because it is an antioxidant and, for example, renders free radicals harmless. Until now, however, strong proof of its protective effects against uranium has been lacking. The Dresden researchers have now made up for this lack. The results are particularly significant because they were obtained from living organisms.
An insoluble and therefore non-toxic complex
The researchers could also gain further insights on how the interaction between heavy metals and glutathione works. Karim Fahmy says, “We see that uranium binds to the carboxyl group of glutathione. This results in an insoluble complex that is no longer toxic.” This applies to the concentrations studied, 10 to 150 micromolar uranium – a content which is typically found at contaminated sites in the German Ore Mountains. Comparative measurements showed that for copper, entirely different reactions occur within the cells. Glutathione fails to deploy any protective effects here.
Measuring metabolic warming for environmentally relevant risk evaluation of heavy metals is intensely promoted at the Institute of Resource Ecology at the HZDR. The unique opportunity to also work with radioactive materials at the institute results in entirely new insights on the effects of low concentrations of radionuclides in organisms, relevant in the fields of medicine and environmental biology.
Publication: Muhammad H. Obeid, Jana Oertel, Marc Solioz, Karim Fahmy, „Mechanism of attenuation of uranyl toxicity by glutathione in Lactococcus lactis“, in: Applied and Environmental Microbiology, June 2016 (doi:10.1128/AEM.00538-16)
Prof. Dr. Karim Fahmy
Institute of Ressource Ecology at the HZDR
Phone +49 0351 260-2952 | Email email@example.com
Christine Bohnet | Press spokesperson
Phone +49 351 260-2450 | Email firstname.lastname@example.org
Helmholtz-Zentrum Dresden-Rossendorf | Bautzner Landstr. 400 | 01328 Dresden, Germany | www.hzdr.de
The Helmholtz-Zentrum Dresden-Rossendorf (HZDR) conducts research in the sectors energy, health, and matter. It focuses its research on the following topics:
• How can energy and resources be used efficiently, safely, and sustainably?
• How can malignant tumors be visualized and characterized more precisely and treated effectively?
• How do matter and materials behave in strong fields and in the smallest dimensions?
The HZDR has been a member of the Helmholtz Association, Germany’s largest research organization, since 2011. It has four locations (Dresden, Leipzig, Freiberg, Grenoble) and employs about 1,100 people – approximately 500 of whom are scientists, including 150 doctoral candidates.
Dr. Christine Bohnet | Helmholtz-Zentrum Dresden-Rossendorf
Cryo-electron microscopy achieves unprecedented resolution using new computational methods
24.03.2017 | DOE/Lawrence Berkeley National Laboratory
How cheetahs stay fit and healthy
24.03.2017 | Forschungsverbund Berlin e.V.
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
24.03.2017 | Materials Sciences
24.03.2017 | Physics and Astronomy
24.03.2017 | Physics and Astronomy