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Effect of intestinal flora in infection protection
The importance of the intestinal flora (microbiome) for the immune system has already been proven by numerous studies. Conversely, the question arises as to how the intestinal flora can be designed so that it offers the widest possible protection against infection. For this, however, first the protective effect of individual bacterial strains must be decoded, which could be done with the help of a new model.
Scientists from the Ludwig Maximillians University (LMU) in Munich, the Technical University of Munich and the University of Vienna have established a mixture of only 15 bacteria in the mouse model, which protects just as well from salmonella as the natural intestinal flora. Based on the model, the interactions of the intestinal flora with the host and pathogens can be specifically investigated for the first time in the future, according to the LMU communication. The researchers published their results in the journal "Nature Microbiology".
The intestinal flora has far-reaching effects on infection protection, which can now be investigated in a new model. (Image: Alex / fotolia.com) Healthy intestinal flora provides good infection protection
The multitude of microorganisms in our intestines form a complex community. "This natural intestinal flora protects very effectively from infections, such as Salmonella or Clostridium difficile, the causative agent of antibiotic-associated diarrhea," reports the LMU. The research team led by LMU biologist Prof. Bärbel Stecher has now "managed to establish a consortium - ie a bacterial community - of only 15 bacterial species in the mouse model, which offers the same protection against infections as the diverse natural gut microbiota."
Interaction of the intestinal flora with the host and pathogens
According to the researchers, the new model will enable targeted studies on the interaction of the gut microbiota with the host and pathogens in the future. This could enable the development of new therapies in the long term, reports the LMU. If, for example, the protective effect of individual bacteria could be determined, the intestinal flora could also be modeled in a targeted manner in order to avoid infections.
Which bacteria cause infection protection?
The technical term for the protective mechanism of the intestinal flora against pathogens is "colonization resistance". Changes in the intestinal flora, such as those caused by the intake of antibiotics, can cancel this colonization resistance, explain the scientists. However, "it remains unclear what role individual bacterial species play in colonization resistance," says Prof. Bärbel Stecher. This is where the new model will help in the future.
Germ-free mice populated with artificial intestinal flora
To decipher the functions of the gut microbiota, the researchers first identified "a minimal consortium of 12 bacterial species" representative of the mouse. Sterile mice were colonized by this consortium known as Oligo-MM-12, but the artificial intestinal flora did not provide the same protection against salmonella as the natural microbiome. Therefore, the scientists looked for a new approach to identify the missing bacteria. For this they used the so-called "Genome-guided-microbiota-design".
Optional anaerobic bacteria of particular importance
"We compared the genetic information of oligo-MM-12 with those of normal complex microbiota and identified the gene groups that are missing in the consortium," explains Prof. Stecher. Above all, characteristic genes for so-called "facultative anaerobic bacteria" were missing. This special group of bacteria can grow optimally in the presence of oxygen, but also thrive without oxygen. Salmonella are also facultative anaerobes, the researchers report. By contrast, the bacteria in the Oligo-MM-12 consortium were predominantly obligate anaerobes for which oxygen is toxic.
Protection against Salmonella comparable to the natural intestinal flora
In the next step, the researchers therefore supplemented the "consortium with three facultative anaerobic bacterial species occurring in the mouse intestine" and subsequently demonstrated experimentally "that only in this combination is a colonization resistance to Salmonella comparable to that of mice with a naturally complex microbiota", reports Prof. Stecher.
Functions of the intestinal flora specifically decipherable?
According to the scientists, the identified consortium and the new principle of "genome-guided-microbiota-design" can play a key role in uncovering previously unknown functions of the gut microbiota. It may also be possible to identify bacterial groups that are suitable for the treatment of disease-related dysfunctions of the intestinal microbiota, the researchers write. (Fp)