Healing Mucosa, interaction of microbial ecology and the immune system

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The maintenance of the stable and healthy symbiosis between microbiota and the host depends on the composition ofthe microbiota which In turn Is controlled by immunological and metabolic factors. Both the Immunological as well as the metabolic synapse are located In the contact zone between microbiota and the host's tissue, the mucus layer. Hence we will focus on the analysis of this specific habitat. It Is reported that the phylogeny and the metabolic functionality are significantly different between the mucus layer and the gut content. The production and maintenance ofthe mucus layer Is known to be strongly affected by Inflammatory diseases like chemically Induces colitis. The Immune response ofthe host Influences directly the composition of the microbiota which then affects metabolic processes. The latter are resulting from the complex metabolic Interdependencles within the microbiota and demand thereby for the analysis of the functional rather than for an assessment of the mere phylogenle diversity. This can be achieved by applying metaproteomlcs and especially protein-stable Isotope probing as a well established variation of metaproteomlcs, In this technique 13C and 15N labelled substrates will be applied and the Incorporation of these Isotopes into proteins determined by high resolution mass spectrometry. The identification of peptides and the according proteins on the basis of metagenome data provides simultaneously phylogenle and functional Information. The degree of Incorporation Is used as a measure of metabolic activity. Furthermore the shape of the isotopologlc distribution allows distinguishing between direct and Indirect metabollsation and hence supports the information on the carbon and nitrogen flux through the microbiota. In addition also the flux from the microbiota Into the host tissue can be assessed. The effect on the metabolic synapse will be also followed by metabolomic profiling ofthe host serum. Since also the endothelium Is crucially Involved in the metabolic synapse and It Is affected by the Inflammatory response we will also analyze the proteomic effects In these cells In colitis In comparison to healthy tissue. The global quantitative proteomics will Indicate the general pathways of the molecular response whereas the phospoproteomlcs approach will lead to Insights Into the cellular signaling Induced by colitis. In summary, we will Identify metabolic pathways and interactions within the mlcroblata and the effect on the metabolic synapse caused by colitis and will combine this with insights Into the response of endothelial cells. Furthermore we will offer proteomic and metaproteomlc support to other subprojects within the SPP.