Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Gut microbiota - Tiny helpers against Samonella

16.06.2017

HZI scientists discover immune mechanism against Salmonella in the mucosa of the gut

Scientists studying infections used to focus mainly on the direct interaction of the immune system with pathogens, but have since moved on to look more closely at the interactions that go on between microbiota, immune system and pathogen. Using mouse models, researchers from the Helmholtz Centre for Infection Research (HZI) recently elucidated a relationship between gut microbiomes of various compositions and the susceptibility to Salmonella infections.


Salmonellae

HZI/ Manfred Rohde / Marc Erhardt

In their study, the scientists from Braunschweig identified several bacterial families that have a protective effect against Salmonella. The researchers also elucidated the immune mechanism in the mucosa of the gut that is regulated by the protective bacterial families. Published in Cell Host & Microbe, the results of the study of the HZI scientists are an important step towards a better understanding of the interactions of the triad of microbiota, immune system and pathogen.

Trillions of microorganisms colonise the surfaces of the human body as permanent, helpful companions. The composition of the so-called microbiota, i.e. the entirety of microorganisms colonising humans and animals, varies very strongly between individuals. Aside from genetic factors, environmental influences - such as nutrition - are the causes of this diversity. The variability of the microbiota has been correlated for some years to the difference in the susceptibility of humans to intestinal infections.

"In recent years, the microbiota has become an ever more important aspect in the research on intestinal diseases. The microbiota fights pathogens in multiple ways: Firstly, the microbiota competes with pathogens for nutrients and thus prevents the colonisation of the host. On the other hand, the protection from pathogens can also be indirect through the triggering of a protective immune response of the host," says Dr Till Strowig, who is the head of the "Microbial Immune Regulation" junior research group at the HZI. "Our study investigated the extent to which the microbiome affects the protection from infection by Salmonella."

The researchers used a mouse model to identify those bacteria of the microbiota that contribute to the protection against Salmonella infection. In the course of this study, they subjected genetically identical mouse lines that differed only in the composition of the microbiota to a Salmonella infection. The weight loss and the survival rate of the mice during the ongoing infection were documented such that both the most sensitive mouse line and the most resistant mouse line were identified by the end of the experiment.
The researchers also used the latest high-throughput sequencing methods to study the differences in the microbial communities of these mouse lines in great detail. Especially the number of certain bacterial families (Prevotallaceae and Verrucomicrobiaceae) was found to be clearly higher in the resistant mouse line as compared to the sensitive mouse line.

Based on these insights, the researchers transplanted several of these bacterial strains to sensitive mice. In response, the mice showed a clearly increased level of protection with respect to Salmonella. "This experiment confirmed that the bacterial composition of the intestinal microbiota plays an important role in the protection from Salmonella infections. And we were able to identify the bacterial families that impart the protection," says Strowig.

The research group also elucidated the underlying mechanism of the protection by these bacteria. It was known from previous studies of other scientists that the immune response to Salmonella involves the production of antimicrobial agents and cytokines - i.e. proteins with an effect on the growth and function of target cells - in an early phase of the immune response.

The mice harbouring the protective bacterial families produced increased amounts of the cytokine, interferon-gamma (IFNγ). This protein plays a critical role in the initiation of immune responses to bacterial pathogens.

Even before infection by Salmonella, the scientist noted a strong increase in the IFNγ production potential of cells of the innate immune system - i.e. the innate lymphocytes - and of the acquired immune system - i.e. the so-called T cells. After infection, these cells also produced increased levels of IFNγ.

"In order to exclude the possibility that other factors might be responsible for the increased resistance to Salmonella, we did another experiment in which we suppressed the IFNγ production by using animal lines that are unable to produce this interferon. Even when the protective bacterial cocktail was added in this experiment, no elevated level of protection was generated," says Strowig.

Unexpected by the researchers, the fight against Salmonella takes place not only on the inside of the gut. Instead, in the case they studied, the microbiota helps the host to fight the pathogens also inside the mucosal tissue of the gut, which the salmonellae need to penetrate for infection. "So the great surprise in our results was not that there is a correlation between the composition of the intestinal microbiota and the course of disease, but the underlying mechanism," says Strowig.

Further studies are planned to find out which of the two types of immune cells - T cells or innate lymphocytes - are more important for the response of the immune system of the intestinal mucosa. The study presented here was done in collaboration with Richard A. Flavell and Andrew L. Goodman (both Yale University, USA) as well as Marc Erhardt (HZI), Ulrich Kalinke (Twincore) and André Bleich (MHH) as local partners.

Original publication:
Sophie Thiemann, Nathiana Smit, Urmi Roy, Till Robin Lesker, Eric J.C., Gálvez, Julia Helmecke, Marijana Basic, Andre Bleich, Andrew L. Goodman, Ulrich Kalinke, Richard A. Flavell, Marc Erhardt, Till Strowig: Enhancement of IFNγ production by distinct commensals ameliorates Salmonella induced disease. Cell Host & Microbe, 2017, http://doi.org/10.1016/j.chom.2017.05.005

The Helmholtz Centre for Infection Research:
Scientists at the Helmholtz Centre for Infection Research (HZI) investigate the mechanisms of infections and of the defences against infections. What is it that makes bacteria or viruses pathogenic? The answer to this question is expected to be key to the development of new medications and vaccines. www.helmholtz-hzi.de

Weitere Informationen:

https://www.helmholtz-hzi.de/en/news_events/news/view/article/complete/gut_micro... - link press release
http://doi.org/10.1016/j.chom.2017.05.005 - link publication
http://www.helmholtz-hzi.de - Webpage of HZI

Susanne Thiele | Helmholtz-Zentrum für Infektionsforschung

More articles from Life Sciences:

nachricht BigH1 -- The key histone for male fertility
14.12.2017 | Institute for Research in Biomedicine (IRB Barcelona)

nachricht Guardians of the Gate
14.12.2017 | Max-Planck-Institut für Biochemie

All articles from Life Sciences >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: Long-lived storage of a photonic qubit for worldwide teleportation

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...

Im Focus: Electromagnetic water cloak eliminates drag and wake

Detailed calculations show water cloaks are feasible with today's technology

Researchers have developed a water cloaking concept based on electromagnetic forces that could eliminate an object's wake, greatly reducing its drag while...

Im Focus: Scientists channel graphene to understand filtration and ion transport into cells

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,...

Im Focus: Towards data storage at the single molecule level

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...

Im Focus: Successful Mechanical Testing of Nanowires

With innovative experiments, researchers at the Helmholtz-Zentrums Geesthacht and the Technical University Hamburg unravel why tiny metallic structures are extremely strong

Light-weight and simultaneously strong – porous metallic nanomaterials promise interesting applications as, for instance, for future aeroplanes with enhanced...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

See, understand and experience the work of the future

11.12.2017 | Event News

Innovative strategies to tackle parasitic worms

08.12.2017 | Event News

AKL’18: The opportunities and challenges of digitalization in the laser industry

07.12.2017 | Event News

 
Latest News

Plasmonic biosensors enable development of new easy-to-use health tests

14.12.2017 | Health and Medicine

New type of smart windows use liquid to switch from clear to reflective

14.12.2017 | Physics and Astronomy

BigH1 -- The key histone for male fertility

14.12.2017 | Life Sciences

VideoLinks
B2B-VideoLinks
More VideoLinks >>>