Direct observation of microorganisms feeding on the intestinal mucosa was successfully made by the microbiology team of David Berry, Alexander Loy and Michael Wagner from the Faculty of Life Sciences, in collaboration with scientists at the Max F. Perutz Laboratories (University of Vienna and the Medical University of Vienna) and with the help of NanoSIMS technology. The results of this research project appear in the current issue of the prestigious journal "Proceedings of the National Academy of Sciences" (PNAS).
To understand the research project by Michael Wagner and his team, one must be ready to follow the microbiologists into the depths of mouse intestine. Michael Wagner, Professor for Microbial Ecology, provides this analogy: "Much like cows grazing in a meadow, intestinal bacteria can feed on mucus secreted by the mucosal tissue. There are a group of microorganisms that do not nourish themselves from mouse food, but rather are specialized in feeding on the secreted products of their host." The intestinal mucus layer is a vital barrier to block pathogenic microorganisms from entering the body and also plays a major role in inflammatory bowel disease. That is why scientists are very interested to know which bacteria inhabit the mucus layer in healthy organisms and thus may suppress the colonization and degradation of this barrier by pathogens.
The team led by Michael Wagner and Alexander Loy wanted to know as part of their activities supported by the Austrian Genome Research Program GEN-AU: Which organisms in healthy mice consider the mucosa and intestinal mucus layer a delicacy? "We've come up with an experimental setup that allows us for the first time to look into the intestine and directly observe organisms grazing on the mucus and measure how much mucus they have taken up," said team leader Alexander Loy from the Department of Microbial Ecology, University of Vienna. To do this, the microbiologists in collaboration with the teams of Thomas Decker, Department of Microbiology, Immunobiology and Genetics at the Max F. Perutz Laboratories and Bärbel Stecher of the University of Munich, labeled an amino acid with stable isotopes that once in the bloodstream mostly ends up in the mucus. Wagner explains, "It became clear from the isotope ratio mass spectrometry measurements made by our collaborators Andreas Richter and Wolfgang Wanek from the Department of Terrestrial Ecosystems Research, University of Vienna, that after only a few hours the isotopes had arrived in the intestinal mucosa, where they were broken down by bacteria." A method was now established to identify bacteria feeding on the mucus layer with single-cell resolution.