für Hygiene und medizinische Mikrobiologie
der Ludwig-Maximilians-Universität München
Pettenkoferstr. 9a
80336 München

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The microbiome and enteric infections

A microbial community of unsurpassed diversity, termed microbiota, colonizes the healthy human intestine. Its various membes include bacteria, viruses and eukaryotes that engage in a physiological network of cooperation and competition and provide numerous functions to its host. An impaired, mature microbiota is able to bloeck colonization of enteric pathogens in a process termed colonization resistance. However, antibiotics, immunosupression and inflammation can disrupt microbial communities and lead to increased susceptibility to pathogen infections. A disturbed (dysbiotic) microbiota is often characterized by depletion of the obligate anaerobic species and a relative enrichment in facultative anaerobic bacteria, in particular members of the Enterobacteriaceae, leading to the definition of "Enterobacterial blooming". The mechanisms driving inflammation-induced blooms include generation of alternative electron acceptors, production of antimicrobial effectors and iron depletion. Inflammation-induced blooms are a potential threat to the human health by promoting infections, the horizontal spread of fitness- and virulence factors, as well as antibiotic-resistances among potential pathogenic species.

Functional gut microbiome research

Due to the enormous complexity of the intestinal microbiota and the lack of appropriate animal models, the mechanisms governing interaction between microbiota, host immune system and pathogens remain largely unclear. We focus on the development of simplified microbial communities, which are employed, in combination with genetic tools for bacteria and the host, to gain mechanistic insights into host-microbe and microbe-microbe interactions at the interface of the host-associated microbiome, immunity and metabolism. Our main focus is on infections with Gram-negative enteric pathogens including Salmonella enterica and pathogenic Escherichia coli, with the following aims:

  1. Understanding interaction of bacterial symbionts with each other and with enteric pathogens;
  2. Analysing how within-host evolution and horizontal gene transfer in the intestinal ecosystem is shaped by microbial interaction, environmental factors, host immune defences and bacteriophages;
  3. Elucidating how inflammatory immune responses and drugs affect the microbiome function, metabolite profiles and bacterial virulence.

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