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Coincidence or main plan?

All living beings – from the simplest animal and plant organisms to the human body – live in close contact with the vast wealth of microbial symbiotes that remain on and in their tissues. Functional co-operation between hosts and microorganisms, which scientists call meta-organism, has only recently become the center of science research. Today, it is clear that many life processes can only be understood in the context of the interaction of organism and symbolization. The aim of the Kiel-based cooperative research center (SFB) 1182 "The emergence and functioning of meta-organisms" at the Christian-Albrechts University in Kiel (CAU) is an understanding of the communication and functional implications of the host microbial relationship.

In addition to studying these interactions, the central issue for SFB 1182 researchers is that the composition of the living organism microbial, ie the totality of its microbial symbiosis, occurs during individual development. It is not clear whether the microbial community is subjected to a functional selection process or whether the random composition of the species is settled. Researching the origin of the microbial composition, the research team of CAU Collaborative Research Center 1182 and the Max Planck Institute for Evolutionary Biology at Plone (MPI-EB) now have the theory of so-called "neutral meta-organisms" across a whole range of model organisms, from very simple creatures to complex vertebrates . Scientists from Kiel and Plone published their findings yesterday in the journal PLOS Biology.

Nulti model of evolutionary theory

One way of handling a very complex individual microbial composition is through theoretical models. The basic model in evolutionary research is the so-called. Neutral null model. It is used to predict population development without selection pressure. Research team SFB 1182 first applied this model to several modeling circular worms to locate mice and compare predictions with experimentally obtained data. "Theory and experimental data are surprisingly good for many organisms. For example, the foreseen composition is also found in the real community of microbial species in a home mouse," Dr. Michael Sieber, a research associate in MPI-EB and a member of SFB 1182, together. "Microbial choice may play a smaller role than previously assumed," Sieber continues.

Map for further microbial research

However, apart from the general good agreement between the neutral model and the actual microbial composition, the researchers also noted significant differences: For example, individual bacteria in the microbial mouse do not correspond to neutral prognosis. Also, the composition of microbial species in the round wound Caenorhabditis elegans does not correspond to the neutral model at all.

"We assume that such deviations from the model and reality could provide traces of specific functions of certain microorganisms," Sieber said. Therefore, the study of system neutral deviations from the neutral model has the potential to meet the key functions of certain bacterial species within the microbial.

Already discusses the initial explanations of deviations from the neutral model. For example, some non-neutral microbial mouse bacteria are functionally involved in the digestion, and their appearance can therefore be the result of a targeted selection process. On the other hand, Caenorhabditis elegans, with a very rapid change of generation, may not live long enough to create a stable, mostly neutral, composition of its microbial. "A model of neutral meta-organism is thus an important theoretical basis for further functional analysis across the spectrum of model organisms explored in our research center regarding species composition and time microbial evolution," said spokeswoman SFB 1182 prof. Thomas Bosch about the importance of work.

Photos are available for download:
Description: Dr. honey. Michael Sieber (left) and prof. Arne Traulsen from the Max Planck Institute for Evolutionary Biology at Plone, along with researchers from Kiel SFB 1182, developed a model of neutral meta-organism.
© Christian Urban, University of Kiel
Description: Researchers have applied a neutral model to several models of organisms studied in SFB 1182, such as round worms or homemade mice. © Science Communication Lab

Video on a neutral meta-organism model:

Press contact:
Christian Urban
Scientific Communication "Kiel Life Science"
Tel.: 0431-880-1974

Additional information:
Center for collaborative research 1182 "Creation and functioning of meta-organisms", CAU Kiel:

Department of Evolutionary Theory,
Max Planck Institute for Evolutionary Biology, Plön:

AG Bosch, CAU Kiel:

scientific contact:
Dr. Michael Sieber
Department for Evolutionary Theory
Max Planck's Institute for Evolutionary Biology, Plön
Tel.: 04522 763-579

Arne Traulsen
Department for Evolutionary Theory
Max Planck's Institute for Evolutionary Biology, Plön
Tel.: 04522 763-239

Thomas Bosch
Zoo Institute, CAU Kiel
Tel.: 0431-880-4170

Original Issues:
Michael Sieber, Lucia Pita, Nancy Weiland-Bräuer, Philipp Dirksen, Jun Wang, Benedikt Mortzfeld, Sören Franzenburg, Ruth A. Schmitz, John F. Baines, Sebastian Fraune, Ute Hentschel, Hinrich Schulenburg, Thomas CG Bosch, Arne Traulsen) Neutrality in the metaorganism. PLOS Biology Published June 19, 2019

idw 2019/06