Guests at EP2
Two French scientists visit RUB labs
Bruno Cailler and Juslan Lo visited the research group EP2 in Bochum from April 1st to April 5th, 2019. Both scientists are working at the Non equilirbium plasma diagnostics laboratory (Diagnostics des Plasmas Hors Equilibre or DPHE) at the INU Champollion in Albi. Juslan Lo is associate professeor and Bruno Caillier is professor.
Juslan Lo received his Master’s Degree in Electrical Engineering and Automation from the Institut National Polytechnique of Toulouse in 2008 and PhD in Plasma Physics and Engineering from Université de Toulouse III in 2012. His main interests include interactions between plasma discharges, electromagnetic waves and biological substrate. During his PhD., he took interest in reconfigurable plasma-based photonic crystals and metamaterials, specially within microwave range frequencies. He joined INU Champollion in 2015 where he currently holds the position of Associate Professor. His current interest is the coupling between high frequency waves and plasma discharges in order to obtain favorable conditions for target species generation for environmental and medical purposes. His visit to Dr. Achim von Keudell's laboratory in University of Bochum was motivated by different experimental plasma characterization setups used in University of Bochum. He is interested in characterizing plasma discharges used in his work.
Bruno Caillier is working on non equilibrium plasmas at low pressure and atmospheric pressure, his interests are DBD lamp, phosphores excited by plasma, surface treatment and optical diagnostics. He is currently working on setting up a monochromator, he is reprogramming the software to control its displacement, set the parameters and acquire the signal. He is also working on the characterization of a DBD plasma lamp (fed with Argon and Krypton) as a UV photon source based on phosphores deposited on the wall of the lamp and excited by plasma. He is also working on international projects in collaboration: University of Sao Paulo in Brazil with the group nano (Grupo de Nanomateriais e Sistemas Luminescentes), CAPES-COFECUB (2020-2024): Plasma synthesis of gold nanoparticles to study the process of energy transfer from excited lanthanides in the infrared in order to search for powerful photo-thermal effects for the development of nanothermometers; with Universidade de Araraquara (UNIARA) in Brazil: Treatment of edible bacterial cellulose with an Aura ECR source, modification of surface properties, adhesion and decontamination. Polymer plasma treatment for cell growth, adhesion modification; with the University of Oran (USTO) in Algeria: Experimental studies of DBD lamp as a UV photon source, thesis in co-supervision with the University of Oran (USTO); with the LGTex laboratory, in Tunisia: Treatment of textile by plasma processes.
GUEST AT EXPERIMENTAL PHYSICS II
Sylvain Iséni stays two weeks for electric field measurements on micro cavity plasma arrays
Dr. Sylvain Iséni stayed from October 21st until October 31st, 2019, in the group of Prof. Achim von Keudell. His visit is part of the collaboration with his home institute, GREMI, espacially, Prof. Remi Dussart. Particularly, the focus of the recent visit is are eletric field measurements by optical emission spectroscopy in the project A6 (Dr. Volker Schulz-von der Gathen, Sebastian Dzikowski) of the CRC 1316. In the project micro cavity arrays are investigated.
Furthermore, Dr. Iséni used the chance to participate in the online seminar and had a talk with the title "Temperate micro-plasmas for environmental purposes: sources, properties, cross-diagnostics & challenges".
GUEST at experimental Physics V at RUB
Emile Carbone visits the research group of Prof. Czarnetzki
On Oktober 25th, 2019, Dr. Emile Carbone from the Max-Planck institute for plasma physics in Garching, Germany, is going to visit the research group of Prof. Czarnetzki. Dr. Carbone is research group leader of the group Plasma for Gas Conversion and is invited to the Ruhr-Universität Bochum in the framework of the CRC 1316. Moreover, he is going to have a seminar talk at experimental physics V about "CO2 dissociation by microwave plasmas: prospects and challenges" at 10:15 in NB 5/158. Everyone who is interested is welcome to join!
RECENT RESEARCH ACHIEVEMENT, project B8
How bacteria protect themselves from plasma treatment
Plasmas are applied in the treatment of wounds to combat pathogens that are resistant against antibiotics. But bacteria know how to defend themselves.
Considering the ever-growing percentage of bacteria that are resistant to antibiotics, interest in medical use of plasma is increasing. In collaboration with colleagues from Kiel, researchers at Ruhr-Universität Bochum (RUB) investigated if bacteria may become impervious to plasmas, too. They identified 87 genes of the bacterium Escherichia coli, which potentially protect against effective components of plasma. “These genes provide insights into the antibacterial mechanisms of plasmas,” says Marco Krewing. He is the lead author of two articles that were published in the Journal of the Royal Society Interface this year.
A cocktail of harmful components stresses pathogens
Plasmas are created from gas that is pumped with energy. Today, plasmas are already used against multi-resistant pathogens in clinical applications, for example to treat chronic wounds. “Plasmas provide a complex cocktail of components, many of which act as disinfectants in their own right,” explains Professor Julia Bandow, Head of the RUB research group Applied Microbiology. UV radiation, electric fields, atomic oxygen, superoxide, nitric oxides, ozone, and excited oxygen or nitrogen affect the pathogens simultaneously, generating considerable stress. Typically, the pathogens survive merely several seconds or minutes.
In order to find out if bacteria, may develop resistance against the effects of plasmas, like they do against antibiotics, the researchers analysed the entire genome of the model bacterium Escherichia coli, short E. coli, to identify existing protective mechanisms. “Resistance means that a genetic change causes organisms to be better adapted to certain environmental conditions. Such a trait can be passed on from one generation to the next,” explains Julia Bandow.
Mutants missing single genes
For their study, the researchers made use of so-called knockout strains of E. coli. These are bacteria that are missing one specific gene in their genome, which contains approximately 4,000 genes. The researchers exposed each mutant to the plasma and monitored if the cells kept proliferating following the exposure.
“We demonstrated that 87 of the knockout strains were more sensitive to plasma treatment than the wild type that has a complete genome,” says Marco Krewing. Subsequently, the researchers analysed the genes missing in these 87 strains and determined that most of those genes protected bacteria against the effects of hydrogen peroxide, superoxide, and/or nitric oxide. “This means that these plasma components are particularly effective against bacteria,” elaborates Julia Bandow. However, it also means that genetic changes that result in an increase in the number or activity of the respective gene products are more capable of protecting bacteria from the effects of plasma treatment.
Heat shock protein boosts plasma resistance
The research team, in collaboration with a group headed by Professor Ursula Jakob from the University of Michigan in Ann Arbor (USA), demonstrated that this is indeed the case: the heat shock protein Hsp33, encoded by the hslO gene, protects E. coli proteins from aggregation when exposed to oxidative stress. “During plasma treatment, this protein is activated and protects the other E. coliproteins – and consequently the bacterial cell,” Bandow points out. An increased volume of this protein alone results in a slightly increased plasma resistance. Considerably stronger plasma resistance can be expected when the levels of several protective proteins are increased simultaneously.
By Meike Drießen, Translated by Donata Zuber
Poster Prize for Christoph Stewig (A3) at the Conference for Plasma Technology 19 in Cottbus
Christoph Stewig was awarded with one of the three poster prizes at the bi-annual conference on plasma technology in Cottbus.