Functional analysis of the molecular cross-talk between methanogenic archaea and the human immune system
Microbial Ecology and Applied Microbiology
Final Report Abstract
Aiming to further deepen our knowledge about the under-estimated immune relevance of archaea we obtained the following results. (i) We elucidated the cellular receptors and mediators that are involved in signaling processes leading to innate immune responses. Using a newly described human myeloid cell line we established a CRISPR/Cas9-based repertoire of clones lacking numerous innate immune receptors, inflammasome components and signal transduction molecules. We were able to demonstrate that the methanogens M. stadtmanae and M. smithii are recognized by single-stranded RNA receptors (predominantly TLR8) through their RNA, initiate an anti-viral immune response and lead to TLR8-dependent alternative inflammasome activation. The strong differences in immune activation by M. stadtmanae vs. M. smithii are unlikely due to differences in their RNA, but rather reflect the differential capacity of human dendritic cells to phagocytose both methanogens. (ii) The general knowledge of the human archeome has been scarce, which is partially due to the overwhelming focus on bacterial species but as well due to methodological challenges since all experimental approaches are optimized for bacteria. To deepen our understanding of the archeome of the human gastrointestinal tract, lung, nose and skin, specific archaea-targeting, PCR-based methods had to be established in close collaboration with the group of Christine Moissl-Eichinger (Graz), demonstrating that detection of archaea is highly dependent on primer selection and in addition on the down-stream sequence processing pipeline. Due to our new protocols, we were able to detect an unexpected high archaeal diversity associated with different body parts. We started to investigate the correlation between the presence and abundance of archaeal species in healthy and diseased individuals, however, the limited number of biopsy samples prevented us from a sound statistical analysis. (iii) Analyzing the ability of M. stadtmanae and M. smithii to form biofilms on diverse surfaces we observed adhesion of both methanogens on abiotic surfaces and strong adhesion of M. stadtmanae on human immune cells as well as on epithelial cell lines during stimulation experiments. In addition, we noticed that, possibly caused by disposal of exopolysaccharides, M. stadtmanae cells easily aggregate in biofilms. (iv) Finally, we studied in addition the newly isolated Methanomassiliicoccus luminyensis strain B10T, a member of the newly identified methanogenic order Methanomassiliicoccales. Due to its capability to degrade trimethylamines, this strain was supposed to be usable as an “Archaebiotic” during metabolic disorders of the human intestine. Overall, M. luminyensis differed from the two other methanoarchaea, M. smithii and M. stadtmanae in respect to sensitivity towards antimicrobial peptides. Similar to M. smithii, it has only weak immunogenic potential and reveals characteristics of a typical commensal gut microbe. Although the pro-inflammatory potential varies from one species to another, the relevance of methanoarchaea for inflammatory processes is not yet clear. Increased abundance of M. stadtmanae was found to frequently correlate with disease and inflammation but also with decreased childhood asthma. Consequently, the question still remains unclear whether this species is directly involved in the development of diseases. Overall more effort and targeted approaches, including clinical studies are needed, and more archaeal isolates are required to perform analyses in appropriate models. The role of the archaeome of the human microbiome, particularly in health and disease, still needs to be explored.
Publications
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(2014) Biofilm formation of mucosa-associated methanoarchaeal strains, Frontiers Microbiol.5 :353
Bang C, Ehlers C, Orell A, Prasse D, Spinner M, Gorb SN, Albers S-V, Schmitz RA
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(2014) The intestinal Archaea Methanosphaera stadtmanae and Methanobrevibacter smithii activate human dendritic cells, PlosOne 9(6):e99411
Bang C, Weidenbach K, GutsmannT, Heine H, Schmitz RA
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(2017) First insights into the diverse human archaeome: specific archaea detection in the gastrointestinal tract, lung, nose and on skin, MBio mBio 8:6 November/December 2017
Koskinen K, Pausan MR, Perras AK, Beck M, Bang C, Mora M, Schilhabel A, Schmitz RA, Christine Moissl- Eichinger C
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(2017) Immunogenic properties of the human gutassociated archaeon Methanomassiliicoccus luminyensis and its susceptibility to antimicrobial peptides, PLOS ONE, 12(10):e0185919
Bang C, T. Vierbuchen T, Gutsmann T, Heine H, Schmitz RA
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(2017) The Human-Associated Archaeon Methanosphaera Stadtmanae is Recognized by Its RNA and Induces TLR8-Dependent NLRP3 Inflammasome Activation" Frontiers in Immunology 8:1535
Vierbuchen T, Bang C, Gutsmann T, Schmitz RA, Heine H
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Archaea as interactive components of complex microbiomes, Trends Microbiol. 2017 Aug 18
Moissl-Eichinger C, Pausan M, Taffner J, Berg G, Bang C, Schmitz RA
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(2018) Archaea – forgotten players in the microbiome, Emerging Topics in Life Sciences 2, 459-468 Biochemical Society/Portland Press
Bang, C, Schmitz RA
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(2018); Metaorganisms in extreme environments: do microbes play a role in organismal adaptation? Zoology
Bang C, Dagan T, Deines P, Dubilier N, Duschl W J, Fraune S, Hentschel U, Hirt H, Hülter N, Lachnit T, Picazo D, Galan P L, Pogoreutz C, Rädecker N, Saad M M, Schmitz R A, Schulenburg H, Voolstra C R, Weiland-Bräuer N, Ziegler M, Bosch T C G
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(2019). "RNA is taking its Toll: Impact of RNA-specific Toll-like receptors on health and disease." Allergy 74(2): 223-235
Vierbuchen T, Stein K, Heine H
