Microorganisms in the human gut are in constant exchange - with each other and with their host. A new study by the Medical University of Graz, published in the journal Nature Communications, now shows how archaea - a previously little-researched group of microorganisms - control this exchange via tiny vesicles. The research was conducted by first author Viktoria Weinberger and Christine Moissl-Eichinger’s team at the Diagnostic & Research Institute for Hygiene, Microbiology and Environmental Medicine.
Communication through mini-packages
Organisms have developed a variety of ways to share important information and spread it across different cells, tissues and organs. In humans, for example, this can happen through hormones or the transmission of stimuli via the nervous system.
But the microorganisms in the human microbiome also need to "talk" to each other and to humans. This happens, among other things, through small membrane-enveloped packages, the so-called vesicles. While vesicles in bacteria have been the subject of intensive research for years, little was previously known about the corresponding mechanisms in archaea.
What are archaea?
Archaea are unicellular microorganisms that form their own domain of life - alongside bacteria and eukaryotes (which include humans). For a long time, they were regarded as ancient oddities that only occur in extreme habitats such as hot springs or salt lakes. Today we know that they also live in less extreme environments, for example in the human gut, where they are responsible for methane production, among other things. There they represent an important, but as yet little researched, component of the microbiome. In contrast to bacteria, archaea differ in their cell structure, their metabolic pathways and their genetic make-up - which makes them an exciting field of research.
How archaea communicate with humans
"We were able to show that intestinal archaea also actively form extracellular vesicles with which they influence their environment," explains Viktoria Weinberger. "These packages contain proteins, nucleic acids, metabolic products and lipids - and are therefore a versatile tool for communicating with other microorganisms or the human immune system."
The team from Graz, together with colleagues from Norwich (UK) and Vienna, has now studied the composition of extracellular vesicles from four different intestinal archaea in detail for the first time.
"Our results provide important evidence that archaea also actively intervene in the molecular communication processes in the intestine," says Christine Moissl-Eichinger, last author of the study. "This opens up completely new perspectives for microbiome research - particularly with regard to the role of archaea in health and disease - and their effect on the immune system." The work was carried out as part of an FWF-funded special research area (SFB) on the topic of "Immunometabolism", which is headed by Thomas Weichhart at the Medical University of Vienna. Interestingly, the vesicles trigger cytokine release in epithelial and immune cells depending on their concentration and depending on the archaeal species or strain.
What’s in the packets?
In addition to a variety of special proteins, the archaeal vesicles also showed interesting metabolites, including the free amino acids glutamate and aspartate, which are already known as neurotransmitters.
it could well be that these archaea actively send us signals - for example via abrupt changes in the intestinal environment," says Christine Moissl-Eichinger. "The question of how these vesicles interact with the immune system and whether they can be used therapeutically, for example as a carrier system for vaccines or drugs, is particularly exciting."
The study thus lays the foundation for a better understanding of how microorganisms not only coexist in the human intestine, but also interact with each other in a targeted manner - with potential effects on immune reactions, metabolic processes and possibly also on diseases such as chronic inflammatory bowel disease or bowel cancer.
Profile: Christine Moissl-Eichinger
Christine Moissl-Eichinger has been a professor at the Medical University of Graz since 2014 and heads a research group at the Diagnostics & Research Institute Institute for Hygiene, Microbiology and Environmental Medicine. Her research focuses on the interaction of microbes with each other and with their environment, e.g. the human body. The focus is on research into the function of archaea in the human gastrointestinal microbiome. She is director of the research initiative BioTechMed Graz, co-director of the Cluster of Excellence "Microbiomes drive Planetary Health" and has recently been awarded an ERC Advanced Grant.
Profile: Viktoria Weinberger
Viktoria Weinberger is a PhD student in the research group of Christine Moissl-Eichinger at the Diagnostic & Research Institute for Hygiene, Microbiology and Environmental Medicine. As part of her dissertation, she is working on archaea from the human intestine. The aim is to better characterize this little-researched group of microorganisms and to investigate their interaction and communication with other microorganisms and the human host, particularly with the immune system.
